The spiders can bite you causing a poison debuff I think. The more that actually bite you, the worse the damage is. I noticed that one time i was taking over 20k per tick and then died after killing the Matriarch.
THIS PART IS FOR THOSE THAT TICK OVER TO REVERED DOING DAILYS AFTER ACQUIRING THIS QUEST BUT BEFORE FINISHING IT:
If you acquire this quest and hit revered before killing the matriarch, you will not be able to see the Matriarch in the halls. This is due to the fact you receive a new questline upon hitting revered. Go back to the Golden Pagoda and you will find an npc with a yellow ! over it's head. There will be three total quests you have to complete from this npc:
Battle Spear of the Thunder King(Battle Spear of the Thunder King)
Battle Helm of the Thunder King(Battle Helm of the Thunder King)
Battle Axe of the Thunder King(Battle Axe of the Thunder King)
After finishing these quests, the halls will phase back into the correct phase and you should be able to complete The Ashweb Matriarch with no issues :).