Cannon Tower is best placed near Sniper Towers so it can take out monsters who will attack the Sniper Tower. It shoots once per second, two times faster than the sniper tower. Due to its fast reload, you can also try placing this tower next to walkways of Blocks where monsters are packed closer together while the Cannon Tower can deal great damage to these monsters. It is not true that the damage increases if the cannon tower kills more monsters. Its only because the cannon tower is affecting more monsters. For example, if the damage shown on top of the cannon tower is two thousand, it is to the group of monster, not to each monster. Cannon tower is weak against high health monsters and flying monsters ( D.A.V.E, Crabatron, Teratorn, Zafretti and Lvl 3+ Fomor ).