Brood Mother Szikalax
From RoR Wiki
This is the first boss you can encounter when you make your way down. It spawns as you get closer to the Big Box of Shinies.
This hero spider is an optional boss. It is not required to kill her to gain access to the last boss.
Brood Mother Szikalax is one of the bosses that can drop various Gunbad jewelry.
Tactic
Masta Wrangla Glix spawns an add group of trolls for every 20% of health he has lost.
The add group gets stronger each time, with the last wave being a group of level 40 champions trolls.
When the last wave hits, the whole group will receive a stun. Defensive morals should therefore be saved for that moment.