From my understanding a straight conversion would have anyone whose got an Origin (e.g. Fey Origin, Immortal Origin, etc) would get transported back to their corresponding plane. However this teleportation function of the pool is meant to be a mystery, and I'm pretty sure if elves and gnomes were getting teleported all the time, people would quickly work it out.
So how would people convert this pool (which I think sounds pretty cool) to 4th edition?
So ignore Origin, and just look at the creature itself. Obviously, elves and gnomes shouldn't be whisked away, nor should devas (arguably). All are creatures of the world, after all.
Things become trickier with eladrin, we'll have to see what story they are given in the EPG/ECG.
Somewhat offtopic:
My players where doing this long dungeon crawl trying to reach an ancient portal before it opens.
the dungeon lower section was connected to a set of natural caves which in the age of monsters used to house a group of orcish gatekeepers druids.
One of the caves contained a lake, in its center was a small island (large enough for one or two medium creatures to stand on).
The entrance to the cave was constintly blocked by regenerative vines.
In the lake dwelt a Blue Slime, it was put there by the Gatekeepers as a kind of a trap: anyone trying to teleport inside the Blue Slime's aura (which covered a large section of the dungeon including the portal area) will instead be redirected to the Blue Slime (as it swims below or around the island, it usually means teleporting to the small island in the lake).
So when the Eladrin PC or the Warlock PC used their teleport in combat - they found themselves alone, away from the party on a small island (potentially facing a Blue Slime which is a solo monster). Since I didn't want to be too cruel, I decided that the teleport redirection will only effect them for 1d4 rounds and then teleport them back to the original destination (which at this time was usually taken by another moob/PC which was somewhat comical).
My players where doing this long dungeon crawl trying to reach an ancient portal before it opens.
the dungeon lower section was connected to a set of natural caves which in the age of monsters used to house a group of orcish gatekeepers druids.
One of the caves contained a lake, in its center was a small island (large enough for one or two medium creatures to stand on).
The entrance to the cave was constintly blocked by regenerative vines.
In the lake dwelt a Blue Slime, it was put there by the Gatekeepers as a kind of a trap: anyone trying to teleport inside the Blue Slime's aura (which covered a large section of the dungeon including the portal area) will instead be redirected to the Blue Slime (as it swims below or around the island, it usually means teleporting to the small island in the lake).
So when the Eladrin PC or the Warlock PC used their teleport in combat - they found themselves alone, away from the party on a small island (potentially facing a Blue Slime which is a solo monster). Since I didn't want to be too cruel, I decided that the teleport redirection will only effect them for 1d4 rounds and then teleport them back to the original destination (which at this time was usually taken by another moob/PC which was somewhat comical).
So ignore Origin, and just look at the creature itself. Obviously, elves and gnomes shouldn't be whisked away, nor should devas (arguably). All are creatures of the world, after all.
Things become trickier with eladrin, we'll have to see what story they are given in the EPG/ECG.
Assuming all PHB races aren't affected, what other races would be affected? Kalashtar? Dal Quori?
Also how could a plot be developed involving the pool? I really like the pool. I'm just somewhat unsure on how to use it.
Following an extremely bad wave of gang wars in the city, the PCs learn that some of the criminal organizations leaders (they are not sure which gangs/leaders) have been possessed by fiends.
The PCs only chance to stop this gang wars and defeat the fiends is to force/trick the possessed leaders to look into the Eldred's Pool waters.
Ways to get the suspected leaders near the pool:
broker true/false truce meetings near the pool. fake arms trading deals or just forcefully grab a gang leader from his gang lair and bring him there.
Following an extremely bad wave of gang wars in the city, the PCs learn that some of the criminal organizations leaders (they are not sure which gangs/leaders) have been possessed by fiends.
hey, that's a good idea. Thanks
Assuming all PHB races aren't affected, what other races would be affected? Kalashtar? Dal Quori?
I don't remember the pool your talking about, but Kalashtar are from the material plane. They are more material than elves. Quori are from Dal Quor, but their hosts are not - it probably mentions specifically what happens to possessed creatures. Note that Quori usually cannot travel to the Material plane, their spirits have to possess a Chosen.
In part, the whole Fey Origin is a fluff that was made game mechanic in 4E. I do not feel Fey Origin really fits Eberron Elves or Gnomes anyway so it may just be scratched and replaced for something else.
Just my 2 copper though.