Teratorn is a powerful monster, His flying ability makes them invulernable to Cannons, Lasers, and Railgun Towers. When paired up with Zafreeti and a high level Fomor, teratorn is almost un-stoppable, with 10 M putty added in, even more so. Teratorns attack increases greatly when he gets the ability to Bounce his fire-balls. But watch out for the enemy's ADTs because that ADTs can easily kill a mob of teratorns, so try to get rid of them before attacking using Teratorns. You can do this by Catapulting them, which isn't effective against a level 6 ADT with level 4 fortification, or catapulting 10 million Putty so the ADT's won't do any damage. You can also use a flying Fomor to reduce the ADT's damage and distract them.
Teratorn can not be put into the Monster Bunker, so they cannot be used for defending.