Encounter Locations
Wintergrasp: Archavon
Behind the portal from Dalaran. Available while your faction controls Wintergrasp.
Dragonblight: Sartharion
Obsidian Sanctum beneath Wyrmrest Temple.
Borean Tundra: Malygos
Highest instance in Nexus. Requires key from Sapphiron.
Naxxramas
Spider Wing: Anub'rekhan - Grand Widow Faerlina - Maexxna
Deathknight Wing: Instructor Razuvious - Gothik the Harvester - Four Horsemen
Plague Wing: Noth the Plaguebringer - Heigan the Unclean - Loatheb
Abomination Wing: Patchwerk - Grobbulus - Gluth - Thaddius
Frostwyrm Lair: Sapphiron - Kel'Thuzad