Grimoire Of Convert Demon

Grimoire Of Convert Demon is the warlock class tome found in Ashran.

Source
This item has a chance to drop from any of the rare elite mobs found in the secondary areas of Ashran.

Trivia
The previous version of this tome was Grimoire of Summoning Secrets - "Your Summon Infernal and Summon Doomguard's cooldown is reduced by 8 minutes."