Goldmine

Goldmine is the master of the Quatro Cerberus Guild.

History
He is old friends with Fairy Tail Guild master Makarov, Blue Pegasus Guild master Bob and Council Member Shitou Yajima. It was shown that they were in one team, so it's very possible that he was a member of Fairy Tail guild.

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. As a message form Mirajane informs Makarov of the formation of Team Natsu, Makarov actually agrees with Goldmine that "Those three" very well could destroy an entire 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 Dragneel, Gray Fullbuster, and Erza Scarlet swiftly defeat the demon but destroy the guild master meeting building in the process. He isn't enraged as everyone else at Team Natsu for this.

Loke arc
He later goes to watch Team Natsu perform the play, Frederick and Yanderica, with Makarov, Mirajane, Bob and Shitou Yajima.