Creeper

In-Game Behavior
When anyone enters the Creeper's view, it will suddenly gain a speed boost and lock-on to the closest player it saw. It'll explode soon after it starts charging, the explosion itself is small but does heavy damage. After the Creeper explodes, it will reconstruct itself shortly after and repeat the process.

EX Form
The Creeper is now transformed into a charged/nitro Creeper. It's at top speed at all times, and it will explode much faster. (It'll explode instantly if you touch it.) It's explosion is a bit bigger, and it also does fatal damage now.