A Dark Emissary can be hired as a Dogs of War unit. They may be hired by Dark Elves, Skaven, Chaos (all types including armies with a daemonic general), Vampire Counts, Tomb Kings, Dwarfs, Empire, Bretonnia (this is an exception to the normal rule), Dogs of War and Orcs & Goblins.
A Dark Emissary costs 265 points and uses up both a Rare choice and a Hero choice.
If fighting alongside a Dwarf army containing an Anvil of Doom, make two separate pools of Power dice in your own Magic phase: one pool to be used with the Anvil (D6+2 dice) and one to be used by the Emissary (two dice plus four for his Level). In your opponent's Magic phase, you can group all your Dispel dice into a single pool.