Mutant Creatures is a mod created by thehippomaster21.
The mod adds a few tough fully-animated mini-bosses that are essentially extreme versions of Minecraft's vanilla mobs.
Each mutant creature drops a special reward when it get killed.
Mutant creatures spawn naturally (but rarely), and can also be spawned by creating Chemical X.
It is compatible with single and multiplayer.
Download Mutant Creatures 1.7.2