Strength: Spider summoning, corrosive healing. Resist Corrosive.
Enemy Behavior: She jumps around a surprising bit. Is capable of spawning a number of Spiders to send after you. She can shoot off Fire Arrows from a bow she summons. She can also send out a swarm of shadow spiders in a ray at you. When you see her dip down to use it, start strafing to one side or the other. She also has the ability to create a burst of fire around herself so be careful when in close.
When she loses one quarter of her total health, she will shield herself and hop onto an upper level of the arena. She will do this again when she is down to one quarter health. Both times she sends a massive number of spiders after you. Thankfully, if she heals above either mark, it does not mean she will perform that action again.