The great coil snake is a mid level treasure chest boss.
Great Coil Snake
Shoots Green Bullets, that do around 55 Damage w/o Armor Effects.
Summons Coil Snake Eggs and Coil Snakes.
Great Temple Snakes
They spawn in eggs, but also can spawn out of the eggs. Shoot a short-range Green projectile, but only does around 20 damage.
Great Temple Snake Egg
Spawns Coil Snakes. If you don't kill it quick, or it will spawn 2-4 Great Temple Snakes.
Normal Bag (85%)
In the chest:
Armor/Weapons Tiers 3-5