Death's Head Caucus

Death's Head Caucus is a Dark Guild that is known for being unmatched in its number of successful assassinations. It seems to be a powerful guild, as all three members shown were able to match or overpower S-Class level Mages such as Natsu Dragneel, Gray Fullbuster, and Juvia Lockser. And their leader, Ikaruga, was able to overpower Erza Scarlet for the majority of their battle.