Demoness

A  is the toughest boss in the game. She is a hidden boss that will give the player an achievement if defeated (along with the Demon).

Contrary to other bosses, it's not required to kill her in order to progress in the game or to get the loot to build a unique item (She does drop the Demon's Skin but this item would usually be looted earlier, from the Demon). However its 20 Sapphire loot is still very useful.

Location
The is located in the Great Cave Go in and go at the very most right, dig if necessary.

Strategies
Using a Particle Sniper Rifle is very useful, going too close is not recommended as well as using a Particle Shotgun, make sure you have a jetpack with you for she is very fast. Building turrets isn't useful AGAINST the boss well maybe using them on some other monsters in the area such as particle birds and hell hounds.