Greetings. I`m a long time D&D player and I kinda dried out of good ideas. I need fresh perspective, some thoughts how to start making new good campaing for low-mid level starting characters (3-5).
I was planning to make a rather unique "outsider" (lesser demonic creature of some sort) , a mixture of demon and devil. He would be sent by Graz'zt, one of Demon Lords who is former Archdevil and now one of the Abyss rulers. That outsider would be sent by specific means to Prime Material Plane (tricked into summoning etc etc), but polimorphed into a shape of common race which dwell in campaign world. In order to advance through the complex devilish hierarchy, he would have to climb the stairs from the least demon towards gaining power through accomplishments and promoting himself all the way towards top.
Sticking that specific character with adventuring party as NPC or henchman was my general idea. Any kind of constructive criticism or good adventure plot is apprechiated!
If you are in doubt, feel free to ask me anything, I would gladly response to any comments.
I would avoid sticking a DM controlled character who is vital to any plot, especially since he is the antagonist (maybe? not sure), right in the party.
Rather make him an ally of the PC's, one that is a driver of adventure for a bit. You could use his guise as a human or what have you, to send the PC's off on "good" heoric adventures that slowly degrade towards more and more vile means.
Or perhaps he sends the PC's off to complete some objective that has a side effect beneficial to the devil.
You really haven't tossed out a "plot", just an NPC idea. What do you want the campaign to be about?
Your question seems to be disjoint, or is that just me?
What do you want your game to be? Are you looking for more than the basics of a plot needed to do your devil-demon guy? Or are you looking for help building a more cohesive world?
As to the first, figure out the NPC's motives and what he needs to do to climb the stairs, and gain more power. What fuels his needs and power? Build encounters to suite. Voila. For example, does the "cambion", for lack of a better term, need a specific item to start his journey? Will he be traveling with the PCs on his missions and if so what is to stop them from killing eachother? Are there enemies the cambion must slay or is his rise just innevitible, are the players going to try and stop him or help him?
To the later, you said you wanted a world for 3-5s. How common are adventurers, how common are 3-5s? If they are rarities then figure out why, if they are relatively common then start figuring out what people of that power level would achieve. My world is a little bit higher level and higher magic tech. Therefore in my worlds the big cities will have constant lights, well funded and regulated guilds, close international ties and info and the average soldier is maybe a level 1-2 fighter. It helps put things into perspective.
Thanks for the tips people.
I was thinking that starting level should be 3-5 (depends on number of players etc) and starting in low populated town or big village for example.
Polis - yeah you are right about that. About the campaign, Orcs are major enemies of human empire and waged wars for over 100 years now.
During the war times, peopel culture and financial state degraded to the point where Rogue Guilds prospered, alot of strange cults/sects shown up and internal political squabbles are daily routine.
Tovec - about "cambion" (yeah closest name I can think of right now too 
, I could put him in a role to use the chaos and disorder to whatever purposes fits him. He would be neutral evil for start, and quite juvenile demon by abysall standards. I was seriously thinking about giving an option for player characters to influence his behaviour and eventually change his alignment towards their own tutoriage (yeah making a good or "noble" demon is rare, but not impossible after all). But that is the case if I do decide to put him into player character party, or in any close connection.
Yeah, starting the campaign in provincial part of the state where war is at hand. Approximately 500 people town where they would start it (also where they could get basic supplies when neccesary). Later, their journey would lead them towards more developed, both industrial and magically rich cities.
In the end, yeah my questions are a bit disjoint I guess since this is basically what I wanted: good story idea and basic adventure plot.
In my experience; wars, social strife, and the like are generally background events that set a tone for the campaign but do not drive the plot.
If you want to use this devil (not sure why you keep referring to the abyss, home of demons) as a main plot point he needs to be pivotol to the campaign somehow. But I will stress do NOT make the campaign about him, it needs to be about the PC's.
Here is a plot hook:
- Fred the Devil approaches the group, claiming to be an oracle. He forsaw the demise of a particular important village, one that is housing an Empire diplomat and spy. The Devil pleads the PC's to investigate the potential reaility of his vision. Meanwhile, he coaxes orcs to attack the village when the PC's arrive; however his real motive is to steal the soul of a priest in the village for his overlord. This particular priest could have made a deal with the devil's overlord, in exchange for protection from the orcs.
The overlord fulfills his side of the bargain by sending the PC's and Fred must collect, even though the orcs attacked because of Fred. This idea looks like a standard type adventure, stock ideas, but is clearly not. The PC's should have to fight the orcs and Fred should steal the priests soul; but the PC's should be suspicious the priest was killed.
Fred the Devil tells the PC's he has seen a shadow in his vision. Something evil in the village they went to. He claims is claiming the lives of any peace bringers (diplomats, etc.).
I'm assuming this is 3/3.5?
Yeah, I do play 3.5 edition right now and for longest time too. The point about that "devil", is that he is originally demon/devil offspring born or spawned in Abyss by tutoriage from Grazzt. He is an ex devil lord who is now demon lord in Abyss and Fred the Devil is his creation, a new breed of demonic creatures.
Yeah, I really like the starting development of the story and expecially how you twisted it around Fred. It will be very hard to determine what is truth from everything, and his visions could be something interesting within the story. Hmm... excellent. The campaign should be good for most of classes I presume, switching through different parts of the story will make all of them useful.
I guess they took away detect evil. That would be a show stopper, eh?
I like the idea of him manipulating the party down the easy path. Hell, all he has to do with most adventurers is lead them to loots and levels and he'll be their best buddy. Seems as deep as most players look at the game.
I like the idea of making him a patron of the party, someone they go to and do missions for. And what he gains eventually will be true minions enslaved to his will. Have him give the party amulets that allow them to communicate with him, using them is difficult at first, tiring (they will just think this means you the DM don't want them overusing this tool)...but thru repeated use it becomes easier to commune with him. Players love devices like that, and they won't suspect at all that each use is bringing their souls under his thumb, bit by bit.
As they start doing questionable acts some players will get suspicious...but our devil has a good reason. You see, there is a devil loose in the world and he is corrupting people, there is no hope for the corrupted and they must be destroyed before this devil becomes too powerful. They will lie and cheat and say anything to assure the people around them that they are good and pure, but inside a festering evil is growing.
He can even give them devices that will detect this evil...well actually it will detect a mark which he has placed upon them, but the dial on the device points to "Evil" becuase thats what he wrote there on the display.
Yes there will be hell to pay.
Oh imagine their suprise when eventually an avatar of one of their good dieties shows up and grabs them by their nose hairs, perhaps even denouncing them...oh thats even better! He shows up and tells them from here on out they are to be shunned and punished for their evil deeds, there is no undoing what has been done. Don't have him explain why, he doesn't care that they have been duped...he can see the darkness on their souls and the evil that they have done.
When they confront their devil patron he will be most concerned! He suspected that there was a monumental shift and power play happening among the gods but he never knew how devasting it was going to be. Clearly this devil they are working against represents the new play for power that the forces of evil are working towards! But the Elder Gods hold firm, they are not easily duped by such blatantly obvious tactics. The players may place their faith in one of the Elder Gods, all their divine gifts will be fueled by the purest gods of the cosmos!
ring ring ring "HELLO MORTAL!?"
"Hey pops its me, Junior."
"Yes oh vileness of my blackest heart, how can I help you with your evil plan?"
"I got a little masquerade proposition for you, it will mean a couple more very strong followers, who's souls I can show you right here....mmm don't they look tasty?"
"Why yes, what would you like me to do to them?"
"Oh nothing much, just pretend you are Elorapril, an Elder God of life and purity. Hand them out some divine power when they call upon it."
"The fools will buy that?!"
"Oh they are in so deep its just stupidly fun and easy to work them...they have no idea of moral goodness, they believe its what I tell them it is. And as long as they get fat loots and gain in abilities they don't care to look any deeper."
"Oh how devilish of you! You do me proud!"
"Thanks pops, you're aces!"...click
That`s excellent Tom Cardin, and thanks for putting up your ideas into motion here! 
I`ll get back when I form out more of the story.
Well, while detect evil COULD spoil things there are spells to make you detect good instead or just slip it in as part of the new breed of demon-devil's powers. Sounds like a solid idea, run with it.
I had an idea, with the new powers of mix-breed, he could mask his alignment or evil aura by taking from those souls he already consumed. For example, if he killed Mark, lev 4 lawful neutral fighter, he could use that fighters alignment to mask his own. Well, that power should have limited uses, like short duration or once per day for example.
I need good devilish name for new monster, this demon/devil mixture. I will make a complete new monster by taking out specific of both races and trying to put up a coherent creature.. which relates to specific monster alignment, habitat, organization etc etc. Any ideas are welcome!
Here is a small progress for Fred the "cambion" (since he will be one of main story NPC`s): Fred was originally created by foul demonic magic, twisted into one creature out of energies from both demonic and devilish flesh. He has yet to show his true worth to his master, by achieving his adulthood through consuming souls of mortals. He was given a small red crystal, which was made out of crystalized blood which runs through Grazz`t domain. The blood of many unearthly denizens has been spilled into that torrent of anguish and suffering. The Crimson shard itself hungers for vengeance and souls from those in his close vicinity and it`s dangerous to use by creatures who are not evil in nature, because it can cause lifetime madness.
Crimson shard (wondrous item):
- only usable by evil creatures (good creatures only: innitial touch contact with the item forces Will saving throw at DC 15, or succumb under permanent Confusion [as per Wizard lev. 4 spell])
- user of the item gains benefits of "special" False Life Spell (wizard lev. 2), which grants 10 bonus hitpoints for every soul obtained. Obtaining the souls can only be used by applying the shard onto the dying creature (-1 to -9 hp).
- if all conditions are met, the item acts as Magic Jar recipent which grows approximately 1/3 of it`s current size everytime it absorbs creature life soul (can contain 5 souls at most, where it reaches the size of fist).
- item stats: hardiness 5/- (protects against any damage), the object has 5 hitpoints. (hardiness and hit points increase with each soul up to 30/-, and 30 hitpoints at max). The fiendish crystal shields itself from harm and once it gets fed, he will not let go of it.
This is just a general description, the item itself has many uses which are to be experimented through out the campaign. It would tempt the characters for using it, perhaps aiding the allies with it`s powers to "heal" (by posessing the stone, you have False Life which can grant you temporary health points) etc etc.
Nice item but its a dead giveaway that the players are really doing evil. I would stay away from items that have evil or questionable function...for the same reason items of solidly good alignment should stay out of the players hands...so that when their alignment switches there is no clue by the items they use ceasing to function for them or actually harming them.
You gotta play this to the hilt. Your true machinations can ONLY be revealed when the players are lost...completely owned by the evils of their own actions. THEN you can have a glorious unveiling of what the characters have truely done.
By that time they should already have destroyed several villages of good people who were all marked by the devil...they should be worshipping an evil devil under the false guise of an Elder God...
Unless they stop at some point and say "hey! This is all too easy, we're levelling, getting loots and killing a lot of people, we haven't killed a monster in ages...something is wrong with the DM, he normally isn't this good to us." At which point perhaps they will look a lot harder at what they are doing, perhaps question more thuroughly one of their victims...but of course they have been told already that all they will spew out are lies.
Then of course they could torture one until they were sure they were getting the truth but hey, that works too, torture is an evil act.