Banning

Towers can be temp-banned or perma-banned. You can make any entity that can inflict banning. Banning removes the tower and all of it's instances from the screen, and makes you unable to use it.

Temp-Ban
A temp-banned tower will be banned for 25 turns, unless the entity says so.

Perm-Ban
A perm-banned tower will be banned for the rest of the game.

Ultra-Ban
This ban is not reversible by anything. It happens in special missions.