Such as?..
No, I'm serious: Demogorgon is a god in Planescape, but Doresain - isn't.
So, how we can be sure?..
Bytopia:
Adamantine Dragon (Dragon #321)
Fire Gnome (Planar Handbook)
(2E) Ethyk (Planes of Conflict/Monstrous Compendium Annual Volume Three)
(2E) Ni'iath (Planes of Conflict)
Beastlands:
Beast Dragon (Dragon #321)
Celestial Wyvern
Dread Blossom Swarm (Monster Manual III)
Gaspar (Planar Handbook)
Hollyphant (Book of Exalted Deeds)
Kadtanach (Dungeon #100)
Spirit of the Wild (Dungeon #148)
Wild Hunter
Xap-Yaup Energon (Planar Handbook)
(2E) Animal Lords - Cat, Hawk, Lizard, Wolf (Planescape Monstrous Compendium Appendix/Monstrous Compendium Outer Planes Appendix)
(2E) Aeserpent (Planes of Conflict)
(2E) Asrai (Planes of Chaos)
(2E) Mortai (Planescape Monstrous Compendium Appendix II/Monstrous Compendium Outer Planes Appendix)
(2E) Oread (Planes of Chaos)
(2E) Warden Beast (Planes of Conflict/Monstrous Compendium Outer Planes Appendix)
Arcadia:
Arcadian Avenger (Monster Manual V)
Chaturani - Pawn, Knight, Bishop, Rook, Queen, King (Dragon #358)
Guardian Familiar (Dangerous Denizens: The Monsters of Tellene)
Rhek (Book of Exalted Deeds)
(2E) Busen (Planes of Law)
(2E) Formian - Worker, Warrior, Myrmarch, Queen (Planes of Law/Monstrous Compendium Annual Volume Three)
(2E) T'uen-rin (Planescape Monstrous Compendium Appendix II/Monstrous Compendium Outer Planes Appendix)
Acheron:
Achaierai
Aspect of Hextor (Miniatures Handbook)
Axiomatic Dragonne (Planar Handbook)
Bladeling (Lord of the Iron Fortress)
Bonespear (Fiend Folio)
Chronotyryn (Fiend Folio)
Justicator (Monster Manual III)
Maug (Fiend Folio)
Reth Dekala (Tome of Battle)
Rust Dragon (Draconomicon)
Siege Beetle (Monster Manual V)
Steelwing (Monster Manual V)
Steel Predator (Fiend Folio)
Xong-Yong Energon (Planar Handbook)
(2E) Fhorge (Planescape Monstrous Compendium Appendix II)
(2E) Hook Spider (Planescape Monstrous Compendium Appendix II)
(2E) Observer (Planescape Monstrous Compendium Appendix II)
(2E) Sword Spirit (Planescape Monstrous Compendium Appendix II)
(1E) Sugo (Dragon #47)
Ysgard:
Aspect of Kord (Miniatures Handbook)
Bariaur (Book of Exalted Deeds/Planar Handbook)
Battle Dragon (Draconomicon)
Fensir (Fiend Folio)
Lillend
Valkyrie (Tome of Battle)
(2E) Asrai (Planes of Chaos)
(2E) Oread (Planes of Chaos)
Pandemonium:
Bloodthorn (Fiend Folio)
Empathos (Dangerous Denizens: The Monsters of Tellene)
Garngrath (Monster Manual V)
Hordlings (Dungeon #124)
Howling Dragon (Draconomicon)
Howler
Mivilorn (Monster Manual III)
Windblades (Monster Manual IV)
(2E) Darkweaver (Planescape Monstrous Compendium Appendix II)
(2E) Murska (Planes of Chaos)
(2E) Miska the Wolf-Spider (Rod of Seven Parts)
(1E) Mapmaker (Dragon #47)
They're in the Fiend Folio and Planescape Monstrous Compendium Appendix II