Cerberus

Equipped creature has +1/+1 and has vigilance. Equipped creature gets "{u}{u}{1}: This creature gets +1/+1 and gets trample until end of turn." and "{u}{x}{x}: This creature gets +1/+1 for each {s} used to cast it. This creature gains +X/+X.", and "If this creature has 3 or more power greater than its base power at the end of combat, exile this artifact."