The master reaverbot of Forbidden Island is a humongous mammoth called Rush Mammoo. It remains buried in a large snow hill until awakened. This reaverbot is the last line of defense for keeping Mistress Sera contained.

Staying out of Rush Mammoo's line of vision through constant circling is a good tactic, but the giant reaverbot will eventually close in, filling the entire field of vision if a digger is not careful to keep some distance.

Rush Mammoo's attacks constist of spitting out ice chunks from its trunk and firing a powerful beam from its underside. The more damage it takes, the faster this reaverbot will move in an attempt to overpower, and its beam will begin making complex turns rather than merely firing straight.