Attacks: Mega Hell Fang, High Hell Fang, Hell Fang
This battle can be real fast. Start off by having Atsuma, Sasquatch, House Guardian, and anyone else in your party. Next, attack Cerberus with everyone except House Guadrian if you can, then ues her EP Drain Dance on Cerberus to lower his EP; if not then attack. Everyone should die except for House Guardian with her, just Drain his EP then attack with Poison shoot, then EP Drain Dance again and so on and so forth, this way he can't attack you and you can finish him off easily.