Fiends of Mystara
by Marco DalmonteWell, first of all let me state that a demon is generally different from a full fledged immortal of the Sphere of Entropy. Both are immortals, but the demons usually have a fixed state and appearance and can only cast specific spells using certain amounts of power (I don't use the rules of WotI but the old rules of gold box slightly modified).
Normal demons are of 7 different types: shrieking, croaking, howling, groaning, hissing, roaring and whispering demons respectively.
Then there are the Entropic lords, like Alphaks (who's an immortal who simply chose to look like a roaring demon), Atzanteotl, Leptar, Hel and even Orcus and Demogorgon are immortals, not just exalted fiends.
The list of the commonly known immortals of Entropy of Mystara is the following (drawn straight from my Guide to Mystaran Immortals):
| Rank | Name | Level | Align. | Portfolio |
| Hierarch | Hel | 36 | C | Chaos, reincarnation, death, lifeforce manipulation |
| Thanatos | 35 | C | Death, decay, destruction, end of all lifeforms | |
| Nyx | 33 | N | Night & darkness, undead, necromancy | |
| Atzanteotl | 31 | C | Corruption, deceit, betrayal, Azcans, humanoids | |
| Eternal | Loki | 30 | C | Hule, deceit, lies, cleverness, theft, betrayal |
| Masauwu | 28 | C | Intrigue, manipulation, corruption | |
| Demogorgon | 26 | C | Demons, undead, destruction | |
| Orcus | 25 | C | Suffering, mass destruction, undead | |
| Talitha | 25 | C | Egocentrism, envy, theft, murder, primal instincts | |
| Empyreal | Set | 21 | C | Hate, vendetta, cruelty, poison, snakelike beings |
| Alphaks | 20 | C | Destroy Alphatians, hate, command over the weak | |
| Corona | 19 | C | Disease, corruption, the Dark Side | |
| Celestial | Ranivorus | 18 | C | Gnolls, raids, folly |
| Arik | 17 | C | Beholders, massacres, folly, nightmares | |
| Skuld | 15 | C | Fury, cruelty, suicide | |
| Jammudaru | 14 | C | Ogres, hate, revenge, brutality, pain | |
| Leptar | 13 | C | Torture, sufferance, oppression, despotism | |
| Temporal | Yagrai | 12 | C | Hobgoblins, orcs, strong will |
| Idris | 11 | C | Vengeance, destroy elves, create perfect draconic race | |
| Brissard | 10 | C | Slavery, deceit, oppression | |
| Bagni Gullymaw | 9 | C | Trolls, cannibalism, violence | |
| Danel | 7 | C | Tiger Clan, betrayal, pain, survival of the fittest | |
| Initiate | Arachne Prime | 6 | C | Slavery, planar spiders, aranea |
| Travestis | 2 | C | Evil woodland beings, poison, deforestation | |
| Saasskas | 1 | C | Devilfishes, conquest, sea undead |
PS: I associated Hircismus (an immortal featured in one of the Immortal modules, IM3 I believe) to Leptar since the two seem to have similar goals and personality.
And that's all I can tell about this, hope it's enough ;)