Rare Spawns
From Hack/Mine Wiki
Rare Spawns
Rare Spawns are about 4x stronger than their normal counterparts. High levels can be dangerous to a low leveled player.
Characteristics
Rare Spawns are usually the same size as the normal mob of their type (except for the occasional ultra-slime). Rare Spawns can be distinguished by color, and they also have a unique name displayed in their health bar, which is colored to correspond to the color of the mob. Along with more health, they are much stronger, and can leave a sizable dent in a rather careless player. They also have a randomly generated name.