Weapon suggestion: Mine

[cpaca]

The mine: Floats on creeper and anticreeper. 
After an amount of time floating on creeper [with a default, but configurable], the mine blows up 
The mine doesn't get destroyed by creeper, as it sticks to the ground below it, and inserts a vacuum to decrease density and float.

[Karsten75]

The mine: Floats on creeper and anticreeper. 
After an amount of time floating on creeper [with a default, but configurable], the mine blows up 
The mine doesn't get destroyed by creeper, as it sticks to the ground below it, and inserts a vacuum to decrease density and float.

You mean something like Conversion Bombs in CW2. except with a no-cost bonus for staying alive an indeterminate time?

[cpaca]

However, the mine just does damage 
no turning it into ac, none of that, just damage.