Serpent is a boss that appears on Wave 6, he has 1800 HP and that increases by 100 for each player. He moves quickly and can weave out of the way of oncoming fire every once in a while. He shoots bursts of 3-5 on 50-100% difficulty, bursts of 7 in 150%, bursts of 8 in 200%, and he just gets much, much better aim in hell difficulty. His weaknesses are that his armor is very exposing - 2x damage + stunned if shot in the legs, and he taunts after three bursts.