Goldmine

Goldmine is the master of the Quatro Cerberus Guild. He apparently is friends with Fairy Tail Guild master Makarov.

Lullaby arc
During the Guild Masters' meeting, Goldmine teases Makarov with the idea that one day his members are going to destroy an entire town one day. As a message form Mirajane informes Makarov of the formation of Team Natsu, Makarov actually agrees with Goldmine that "Those three" very well could destroy an intire town.

Later, as Kageyama tries to use lullaby on the guild masters, all the guild masters have a plan to convince him to stop. However, they all cower as the flute turns into a giant demon named Lullaby that wants to kill everyone. Goldmine then stands by as Natsu Dragoneel, Gray Fullbuster, and Erza Scarlet swiftly defeat the demon but destroy the guild master meeting building in the process. He is as enraged as everyone else at Team Natsu for this.