Mamma Longlegs

Spawn cannot be blocked. Part of the Spider Nest Mini World Change. After having killed it three times, you will not be able to enter the area anymore.Kill it three times for the achievement Nestling.

Similar to a Hydra but with weaker healing.

All depends on your level. If you are a high level you can just run around and combo rod/wand with exori mort or just using Sudden Death. If you are a lower level the best thing to defeat this boss is using Fire Field and run around it while attacking. Another alternative is to use Fire Wall and move across the middle square causing Mamma to run around the top or bottom of the wall, this is the most effective way to kill her at low levels Paladins may want to use a shield, and Assassin Stars to kill it fast.