Can You Convert Call of Cthulhu RPG to 5th Edition D&D? - Downloaded from the Wizards Community, all coding removed by Solauren

Post/Author/DateTime	Post
#1 Sands666 Aug 02, 2015 13:49:43	I was wondering if anyone ever player the d20 version of Call of Cthulhu and if so, if you think that it would be possible to convert CoC to 5e successfully. There was an article released a couple of months back that had a loose conversion for 5e Modern on the Wizards site, so maybe that could be of some help. I sense that some of the challenges would remain even with Modern, where levels and high HP in the d&d system could take away from some of the fear/horror elements. The main reason im interested in eventually trying to convert CoC to 5e is because my players seem to get tired of learning new rules systems. I've never played Caosiums CoC at all, but I've been reading Lovecraft lately and listened to the Podcast Cthulhu & Friends. I think CoC has potential for 5e though. Does anyone know where I can even find the d20 version on PDF?
#2 ankiyavon Aug 02, 2015 15:10:42	I've never played it, but it should be possible. CoC d20 is based on the OGL, which is to say, 3rd edition, and converting 3E stuff to 5E is entirey doable. As far as actually finding a pdf copy, I looked around for a bit, and couldn't find one, which surprised me! The Chaosium version is available on drivethrurpg if that's close enough.
#3 Ath-kethin Aug 02, 2015 19:08:58	The D20 CoC was amazing. Easily one of the best books from the 3e era. Converting it to 5e would be a challenge, thought, since it does not use PHB classes at all. 5e mechanics would work OK - better than 3e em hanics in some ways - but converting classes will be a challenge. CoC used its own spellcasting system as well, and without the sourcebook those conversions would be impossible. And the book is almost worth it for the d20 monster and Great Old One stats alone. I don't know about PDFs, but you can pick up the hardcover off amazon for $40 or so. Good luck.
#4 Imaculata Aug 03, 2015 2:38:08	Well, you can definitely keep the old sanity system from the 3.5 Call of Cthulhu book (I happen to have it in front of me right now, and feel lucky to own one). As far as spellcasting goes, in D20 CoC spells deal either sanity damage, or temporary abiliity damage to the caster. There's only a few very powerful spells that cause permanent ability drain on the caster. A spell can also be casted by multiple casters, in which case the ability damage (if any) is distributed equally among all casters, but they all suffer the full sanity damage cost (if any). When casters work together, one caster is always considered as the leader, for the purpose of determining the range and other data. I don't know exactly how ability damage and caster levels work in 5e edition, and if they exist at all. As for converting monsters, some monsters may have a 5e equivalent, such as a common human cultist, or a zombie or skeleton. But others are way out there, and don't really use a standard template as far as I know. You can keep the sanity costs the same, but may have to tweak the health, AC, saves and ability points a bit. You can also convert some of the stuff from OGL Horror, which also uses the 3.5 system. I recently posted an extended list of weapons for a D20 modern zombie campaign in this topic. It's basically the list from OGL Horror, but with additional weapons, cool pictures, a price listing (no wealth system), and a more easy to read lay out. But some of the weapons in this list have special rules, and require that you own the OGL Horror source book. These are of course all modern firearms and power tools, and would probably not be suitable for a Cthulhu campaign that takes place in the past. You can however use the improvized weapon examples, which are really handy, and should be easy to adapt for 5e.
#5 shintashi Aug 04, 2015 21:04:21	converting the old ones is going to be a bit of a perplexing task, as their attributes were very high. Take Tiamat's proficiency modifier of +9, for instance. Doubled it is +18, and then add +8 from Wisdom. You get 26. now add a base of 10, and you get passive perception 36. That's an example of how the stats are constructed. If you have Deities and Demigods from AD&D, you can find any of their attributes, add +5, and get the 5th edition values. For example, if it says 23 Wisdom, that becomes a 28 wisdom in 5th edition. 3rd edition hit points are higher than 5th edition hit points. For about every 700 hit points in 3rd edition, you get about 500 hit points in 5th edition, but that's mostly from lower constitution bonuses. So if the Old One has 1400 hit points in d20, they have about 1000 in 5th edition. Old Ones regardless of the form they take should be rolling d20s for hit points. If they have a constitution score above 20, you might as well give them Maximum on their die rolls, or just roll more dice. 27-33d20 is pretty standard for demigod level encounters. That crudely fits a hit dice matrix like this 30 hit dice: demi 35 hit dice: lesser 40 hit dice: intermediate 45+ hit dice; greater When converting, treat 2d12 as 3d8, or 2 hit dice of d20 in 5th edition, so the hit dice for the various d20 conversions looks something like this: Azathoth: 72d8 = 24x3 = 24x2d12 = 48d20 hit dice. We will get to stats over 50 in a bit... Cthulhu: 42d12 = 42d20 hit dice Hastur: 40d12 = 40d20 hit dice Nyarlathotep 35d8 = 11.66x3 = 23.33d20 hit dice, or 24 hit dice Shub Niggurath: 53d8 = 36d20 hit dice Yog Sothoth: 60d8 = 40d12 = 40d20 hit dice Now, if a stat is really high in 3rd edition, we pretty much ruled it something like this: AD&D. . . 3e 19. . . . . .20 20. . . . . .25 21. . . . . .30 22. . . . . .35 23. . . . . .40 24. . . . . .45 25. . . . . .50 but you might have a stat that's higher than normal. Sure, there's a lot of ways to do it. The 26 strength from AD&D was converted into a 92 in 3rd ed, but skipping that silliness for a bit, let's expand the previous table AD&D. . . 3e. . . .5e. . .Bonus 19. . . . . .20. . . .19. . . . +4 20. . . . . .25. . . .20. . . . +5 21. . . . . .30. . . .22. . . . +6 22. . . . . .35. . . .24. . . . +7 23. . . . . .40. . . .26. . . . +8 24. . . . . .45. . . .28. . . . +9 25. . . . . .50. . . .30. . . . +10 25. . . . . .55. . . .32. . . . +11 25. . . . . .60. . . .34. . . . +12 25. . . . . .65. . . .36. . . . +13 25. . . . . .70. . . .38. . . . +14 25. . . . . .75. . . .40. . . . +15 25. . . . . .80. . . .42. . . . +16 25. . . . . .85. . . .44. . . . +17 25. . . . . .90. . . .46. . . . +18 25. . . . . .95. . . .48. . . . +19 25. . . . . .00. . . .50. . . . +20 Now these bonuses line up fairly similar to the BECMI immortal gold book rules with Attributes up to 100, and 20d6 damage punches. BECMI immortals were known to make strength checks to move planes of existence. so Azathoth's Constitution in 5th edition, being an entity from beyond the traditional planes, like the far realm or where black balls come from, we have no legitimate reason to stick with Bounded accuracy for them. Therefore, 69 Constitution is in the +13 category, +14 if you want to round up. So rounding up, you get 48d20 +672, Tiamat averages 10.5 hit points per hit die, so 504 +672 = 1176 hit points. Nyarlathotep's Wisdom of 80 converts to a 42 in 5th edition, and a +16 base bonus. CR 30 is a +9 bonus, and every 4 CR is about +1, so setting Azathoth up as CR 48 would put him at 20 CR over CR 28, or +5 more Proficiency Bonus, Which comes to a +14, and gives him a Constitution Save of +28. Nyarlathotep's CR would be 24 or 30 if you count his spell like abilities, so a +7 proficiency bonus doubled is +14 and with the +16 wisdom bonus puts us at +30 perception, 40 passive perception, which is well within the realm of impossible. If we assumed a +9 or better proficiency, we would have a Passive perception of 44. I hope that helped.
#6 Imaculata Aug 05, 2015 1:47:13	That is brilliant. I have no idea how you figured all that out, but that is really impressive. But how would that work for their saves and armor classes?
(Reply to #6) shintashi	Imaculata wrote:
(Reply to #7) dave2008	shintashi wrote:
(Reply to #5) dave2008	shintashi wrote:
#10 Tempest_Stormwind Aug 14, 2015 11:17:57	dave2008 wrote:
(Reply to #10) dave2008	Tempest_Stormwind wrote:
#12 Imaculata Aug 15, 2015 5:13:40	Very impressed by the stat conversion. I don't know if its accurate, since my knowledge of 5th edition rules is limited, but great job none the less.
#13 shintashi Aug 15, 2015 12:20:36	dave2008 wrote:
#14 dave2008 Aug 15, 2015 16:03:07	I was a big fan of the I in BEMCI, I still have my original copy. I think you are overstating how the "outer gods/ old ones" fit into that Cosmos. Not to mention the fact that you chart is comparing 5e to AD&D, not D&D. The Immortal rules topped out at 100 stats if I remember correctly, and though it does have the great barrier (or what ever it was called), and it was implied that this is where gods that advanced past Heirarch go, I certainly don't recall any connection to old ones similar in nature to lovecraft's mythos. On a side note, you know the original "Dieties and Demigods" included the Cthulhu mythos. My friend had copy of it before it got cancelled because they didn't have the rights. Luckily I've got a scan of it, so I can give you the stats in AD&D for Cthulhu, Azathoth, etc. if you want them.
(Reply to #14) shintashi	dave2008 wrote:
#16 shintashi Aug 15, 2015 17:09:10	ok, i got a hold of the immortal rules, it's been a while, im really rusty, but here ya go, context: "For example, when used to find the seventh dimension, or the hiding place of the Old Ones, this effect leads in a random direction." don't read past this point if you don't want to know the awesome that is the Immortal Rules... Show "Coming from a place now lost in the mists of forgotten time and memory, the first Immortals found the multiverse; they did not create it. They found it without order, and without purpose...Someone must have been here before, they reason. Someone or some group, or perhaps some thing, made all of this . The Immortals call them the Old Ones—beings to whom even the power of the Immortals is but a drop in an ocean. The Immortals are correct. With such power, the Old Ones knew that the Immortals would come. They saw this as an opportunity . For despite their unimaginable abilities, the Old Ones are tragically similar to Immortals in one respect. They cannot reproduce and the only way for other beings to achieve their level of power is through a test of time, experience, and will. Just as Immortals await and desperately desire the appearance of exceptional mortals, so do the Old Ones watch and wait for the greatest and best of all the Immortals." "Withdrawing themselves into the sixth and higher dimensions, the Old Ones created a type of wall between themselves and the rest of existence. Whenever an Immortal tries to pass beyond the first five dimensions, he or she enters a special realm. Immortals perceive this realm as a whirlpool of infinite size. made of a watery form of ether. Some Immortals have been lost in the huge swirling mass for many years; they are known to still live, but are missing, and presumed unrecoverable." "imply called vortex creatures by Immortals, these beings are powerful and greatly feared. The Immortals believe that the vortex creatures are servants of the Old Ones, sent to observe, correct, or destroy. In creating the barrier, the Old Ones knew that its existence would produce certain odd effects—most notably the evolution of life forms with a new dimensional viewpoint, the Nightmare creatures. They saw this as another opportunity. Immortals have begun to look at Nightmare creatures as an alternate stock from which Immortals may arise once they have reached the level of evolution of the Normal dimensional creatures. The barrier will not be removed until this great experiment of the Old Ones has reached a conclusion, for it has been successful in creating new Old Ones." "They saw the coming of the blackballs as their punishment and final destruction, and the other Immortals still believe that this is what occurred. But unbeknownst to all, they passed beyond the barrier, and exist now with the Old Ones." "The Old Ones are prepared to wait indefinitely, for Time has no hold over them. If any player character succeeds in the great journey, not merely achieving Hierarch status but proving his or her superiority by doing it twice—well, no higher goal can be attained, and no reward is too great. The player wins and his character vanishes. And that is the final end of this game. One fact remains for you, as Dungeon Master, to decide. Who are the Old Ones? Are they indeed the greatest and most powerful beings of all? Or perhaps, as they wait secure in their power, do even the Old Ones naively fail to see the most obvious fact of all? Can they really believe that no higher Being watches them? One who also watches... and waits..."
(Reply to #16) dave2008	shintashi wrote:
(Reply to #15) dave2008	shintashi wrote:
(Reply to #15) dave2008	shintashi wrote:

Post/Author/DateTime

Post

Sands666

Aug 02, 2015 13:49:43

I was wondering if anyone ever player the d20 version of Call of Cthulhu and if so, if you think that it would be possible to convert CoC to 5e successfully.

There was an article released a couple of months back that had a loose conversion for 5e Modern on the Wizards site, so maybe that could be of some help. I sense that some of the challenges would remain even with Modern, where levels and high HP in the d&d system could take away from some of the fear/horror elements.

The main reason im interested in eventually trying to convert CoC to 5e is because my players seem to get tired of learning new rules systems.

I've never played Caosiums CoC at all, but I've been reading Lovecraft lately and listened to the Podcast Cthulhu & Friends.

I think CoC has potential for 5e though. Does anyone know where I can even find the d20 version on PDF?

ankiyavon

Aug 02, 2015 15:10:42

I've never played it, but it should be possible. CoC d20 is based on the OGL, which is to say, 3rd edition, and converting 3E stuff to 5E is entirey doable.

As far as actually finding a pdf copy, I looked around for a bit, and couldn't find one, which surprised me! The Chaosium version is available on drivethrurpg if that's close enough.

Ath-kethin

Aug 02, 2015 19:08:58

The D20 CoC was amazing. Easily one of the best books from the 3e era. Converting it to 5e would be a challenge, thought, since it does not use PHB classes at all. 5e mechanics would work OK - better than 3e em hanics in some ways - but converting classes will be a challenge. CoC used its own spellcasting system as well, and without the sourcebook those conversions would be impossible. And the book is almost worth it for the d20 monster and Great Old One stats alone. I don't know about PDFs, but you can pick up the hardcover off amazon for $40 or so. Good luck.

Imaculata

Aug 03, 2015 2:38:08

Well, you can definitely keep the old sanity system from the 3.5 Call of Cthulhu book (I happen to have it in front of me right now, and feel lucky to own one). As far as spellcasting goes, in D20 CoC spells deal either sanity damage, or temporary abiliity damage to the caster. There's only a few very powerful spells that cause permanent ability drain on the caster. A spell can also be casted by multiple casters, in which case the ability damage (if any) is distributed equally among all casters, but they all suffer the full sanity damage cost (if any). When casters work together, one caster is always considered as the leader, for the purpose of determining the range and other data.

I don't know exactly how ability damage and caster levels work in 5e edition, and if they exist at all.

As for converting monsters, some monsters may have a 5e equivalent, such as a common human cultist, or a zombie or skeleton. But others are way out there, and don't really use a standard template as far as I know. You can keep the sanity costs the same, but may have to tweak the health, AC, saves and ability points a bit.

You can also convert some of the stuff from OGL Horror, which also uses the 3.5 system. I recently posted an extended list of weapons for a D20 modern zombie campaign in this topic. It's basically the list from OGL Horror, but with additional weapons, cool pictures, a price listing (no wealth system), and a more easy to read lay out. But some of the weapons in this list have special rules, and require that you own the OGL Horror source book. These are of course all modern firearms and power tools, and would probably not be suitable for a Cthulhu campaign that takes place in the past. You can however use the improvized weapon examples, which are really handy, and should be easy to adapt for 5e.

shintashi

Aug 04, 2015 21:04:21

converting the old ones is going to be a bit of a perplexing task, as their attributes were very high. Take Tiamat's proficiency modifier of +9, for instance. Doubled it is +18, and then add +8 from Wisdom. You get 26. now add a base of 10, and you get passive perception 36.

That's an example of how the stats are constructed. If you have Deities and Demigods from AD&D, you can find any of their attributes, add +5, and get the 5th edition values. For example, if it says 23 Wisdom, that becomes a 28 wisdom in 5th edition. 3rd edition hit points are higher than 5th edition hit points. For about every 700 hit points in 3rd edition, you get about 500 hit points in 5th edition, but that's mostly from lower constitution bonuses. So if the Old One has 1400 hit points in d20, they have about 1000 in 5th edition. Old Ones regardless of the form they take should be rolling d20s for hit points. If they have a constitution score above 20, you might as well give them Maximum on their die rolls, or just roll more dice. 27-33d20 is pretty standard for demigod level encounters. That crudely fits a hit dice matrix like this

30 hit dice: demi

35 hit dice: lesser

40 hit dice: intermediate

45+ hit dice; greater

When converting, treat 2d12 as 3d8, or 2 hit dice of d20 in 5th edition, so the hit dice for the various d20 conversions looks something like this:

Azathoth: 72d8 = 24x3 = 24x2d12 = 48d20 hit dice. We will get to stats over 50 in a bit...

Cthulhu: 42d12 = 42d20 hit dice

Hastur: 40d12 = 40d20 hit dice

Nyarlathotep 35d8 = 11.66x3 = 23.33d20 hit dice, or 24 hit dice

Shub Niggurath: 53d8 = 36d20 hit dice

Yog Sothoth: 60d8 = 40d12 = 40d20 hit dice

Now, if a stat is really high in 3rd edition, we pretty much ruled it something like this:

AD&D. . . 3e

19. . . . . .20

20. . . . . .25

21. . . . . .30

22. . . . . .35

23. . . . . .40

24. . . . . .45

25. . . . . .50

but you might have a stat that's higher than normal. Sure, there's a lot of ways to do it. The 26 strength from AD&D was converted into a 92 in 3rd ed, but skipping that silliness for a bit, let's expand the previous table

AD&D. . . 3e. . . .5e. . .Bonus

19. . . . . .20. . . .19. . . . +4

20. . . . . .25. . . .20. . . . +5

21. . . . . .30. . . .22. . . . +6

22. . . . . .35. . . .24. . . . +7

23. . . . . .40. . . .26. . . . +8

24. . . . . .45. . . .28. . . . +9

25. . . . . .50. . . .30. . . . +10

25. . . . . .55. . . .32. . . . +11

25. . . . . .60. . . .34. . . . +12

25. . . . . .65. . . .36. . . . +13

25. . . . . .70. . . .38. . . . +14

25. . . . . .75. . . .40. . . . +15

25. . . . . .80. . . .42. . . . +16

25. . . . . .85. . . .44. . . . +17

25. . . . . .90. . . .46. . . . +18

25. . . . . .95. . . .48. . . . +19

25. . . . . .00. . . .50. . . . +20

Now these bonuses line up fairly similar to the BECMI immortal gold book rules with Attributes up to 100, and 20d6 damage punches. BECMI immortals were known to make strength checks to move planes of existence.

so Azathoth's Constitution in 5th edition, being an entity from beyond the traditional planes, like the far realm or where black balls come from, we have no legitimate reason to stick with Bounded accuracy for them. Therefore, 69 Constitution is in the +13 category, +14 if you want to round up.

So rounding up, you get 48d20 +672, Tiamat averages 10.5 hit points per hit die, so 504 +672 = 1176 hit points.

Nyarlathotep's Wisdom of 80 converts to a 42 in 5th edition, and a +16 base bonus. CR 30 is a +9 bonus, and every 4 CR is about +1, so setting Azathoth up as CR 48 would put him at 20 CR over CR 28, or +5 more Proficiency Bonus,

Which comes to a +14, and gives him a Constitution Save of +28.

Nyarlathotep's CR would be 24 or 30 if you count his spell like abilities, so a +7 proficiency bonus doubled is +14 and with the +16 wisdom bonus puts us at +30 perception, 40 passive perception, which is well within the realm of impossible. If we assumed a +9 or better proficiency, we would have a Passive perception of 44.

I hope that helped.

Imaculata

Aug 05, 2015 1:47:13

That is brilliant. I have no idea how you figured all that out, but that is really impressive. But how would that work for their saves and armor classes?

(Reply to #6)

shintashi

Imaculata wrote:

(Reply to #7)

dave2008

shintashi wrote:

(Reply to #5)

dave2008

shintashi wrote:

#10

Tempest_Stormwind

Aug 14, 2015 11:17:57

dave2008 wrote:

(Reply to #10)

dave2008

Tempest_Stormwind wrote:

#12

Imaculata

Aug 15, 2015 5:13:40

Very impressed by the stat conversion. I don't know if its accurate, since my knowledge of 5th edition rules is limited, but great job none the less.

#13

shintashi

Aug 15, 2015 12:20:36

dave2008 wrote:

#14

dave2008

Aug 15, 2015 16:03:07

I was a big fan of the I in BEMCI, I still have my original copy. I think you are overstating how the "outer gods/ old ones" fit into that Cosmos. Not to mention the fact that you chart is comparing 5e to AD&D, not D&D. The Immortal rules topped out at 100 stats if I remember correctly, and though it does have the great barrier (or what ever it was called), and it was implied that this is where gods that advanced past Heirarch go, I certainly don't recall any connection to old ones similar in nature to lovecraft's mythos.

On a side note, you know the original "Dieties and Demigods" included the Cthulhu mythos. My friend had copy of it before it got cancelled because they didn't have the rights. Luckily I've got a scan of it, so I can give you the stats in AD&D for Cthulhu, Azathoth, etc. if you want them.

(Reply to #14)

shintashi

dave2008 wrote:

#16

shintashi

Aug 15, 2015 17:09:10

ok, i got a hold of the immortal rules, it's been a while, im really rusty, but here ya go, context:

"For example, when used to find the seventh dimension, or the hiding place of the Old Ones, this effect leads in a random direction."

don't read past this point if you don't want to know the awesome that is the Immortal Rules...

Show

"Coming from a place now lost in the mists of forgotten time and memory, the first Immortals found the multiverse; they did not create it. They found it without order, and without purpose...Someone must have been here before, they reason. Someone or some group, or perhaps some thing, made all of this . The Immortals call them the Old Ones—beings to whom even the power of the Immortals is but a drop in an ocean. The Immortals are correct. With such power, the Old Ones knew that the Immortals would come. They saw this as an opportunity . For despite their unimaginable abilities, the Old Ones are tragically similar to Immortals in one respect. They cannot reproduce and the only way for other beings to achieve their level of power is through a test of time, experience, and will. Just as Immortals await and desperately desire the appearance of exceptional mortals, so do the Old Ones watch and wait for the greatest and best of all the Immortals."

"Withdrawing themselves into the sixth and higher dimensions, the Old Ones created a type of wall between themselves and the rest of existence. Whenever an Immortal tries to pass beyond the first five dimensions, he or she enters a special realm. Immortals perceive this realm as a whirlpool of infinite size. made of a watery form of ether. Some Immortals have been lost in the huge swirling mass
for many years; they are known to still live, but are missing, and presumed unrecoverable."

"imply called vortex creatures by Immortals, these beings are powerful and greatly feared. The Immortals believe that the vortex creatures are servants of the Old Ones, sent to observe, correct, or destroy.
In creating the barrier, the Old Ones knew that its existence would produce certain odd effects—most notably the evolution of life forms with a new dimensional viewpoint, the Nightmare creatures. They saw this as another opportunity. Immortals have begun to look at Nightmare creatures as an alternate stock from which Immortals may arise once they have reached the level of evolution of the Normal dimensional creatures. The barrier will not be removed until this great experiment of the Old Ones has reached a conclusion, for it has been successful in creating new Old Ones."

"They saw the coming of the blackballs as their punishment and final destruction, and the other Immortals still believe that this is what occurred. But unbeknownst to all, they passed beyond the barrier, and exist now with the Old Ones."

"The Old Ones are prepared to wait indefinitely, for Time has no hold over them. If any player character succeeds in the great journey, not merely achieving Hierarch status but proving his or her superiority by doing it twice—well, no higher goal can be attained, and no reward is too great. The player wins and his character vanishes. And that is the final end of this game. One fact remains for you, as Dungeon
Master, to decide. Who are the Old Ones? Are they indeed the greatest and most powerful beings of all? Or perhaps, as they wait secure in their power, do even the Old Ones naively fail to see the most obvious fact of all? Can they really believe that no higher Being watches them? One who also watches... and waits..."

(Reply to #16)

dave2008

shintashi wrote:

(Reply to #15)

dave2008

shintashi wrote:

(Reply to #15)

dave2008

shintashi wrote: