This tower rapidly saps the health of all poison-susceptible units within its range. Its damage must be applied many times per second as an upgraded snake tower can do several thousand points of damage to a hero over the course of just a few secon.
A careful attacker can often pass a snake tower without taking damage, letting cannons mop it up later. For this reason, it's a good idea to use them to cover firebolt towers, punishing heroes who come within their range to attack with a spell.
A level 9 Snake Tower can withstand one level 6 Sonic Blast spell cast.