Blink out of the webs, and start summoning a spider demon. A big, hungry, other-spider-eating spider demon.
You blink out of the web, leaving some feathers behind. You are in a different room now, surrounded once more by webbing, but not ensnared.
You caw loudly three times to call forth your demon, and a portal begins to appear. As do half a dozen of the giant spiders.
(sorry I'll be better about that)
"Well shit" Charge down the stairs and get between the spiders and my furry companion fighting defensively e.g. stab anything that approches
"Samuel get the bird free" (If successful Korvash) started saying before the bird disappeared from the web and started channeling magic in mid air"never mind."
Edited
Your way down is blocked by the swarm. You stab frantically ,but the mass is pretty thick, and you feel the tip of the spear sliding off armor, or the haft getting caught, or you are jostled each time you swing. Bad news is, you are being bitten by these spiders. Good news - for everyone else - is that you have caused a bit of a jam, blocking the advance of the spiders into the room. Of course, there are still a fair number of them already in the room, so the drowned one still has work to do as well.
((I guess Corvo will save himself somehow. Also I didn't expect the bar to be so big, so I guess I don't pick up the bar.))
"Na, don't get the bloody guards. Everything'll be jake, he said." The drowned One mumbles.
I'll use my magic on as many enemies as I can. The enemy reacts as if they suddenly are underwater, however they don't drown (that would be a bit powerful). They are slowed down, they don't attack as hard. Animals also freak out. (Imagine a spider struggling through water). I call this spell "Woeful Water).
hmm. Well, these aren't aquatic spiders, so this could work. Now, "kill it with water" is totally a valid tactic here - I believe it is well within your character concept. So I don't see it as OP. but if you wish to be limited in that way, I'm good with that too. You cast, and water slowly seeps out around your legs, pooling at your feet and spreading. You get an inch or two of water in the room.the spiders seem unfazed. Some barely register your existence at all, heading outward. A few head straight for you though.
Wake up and smell the coffee spider entrails.
((Edit: Just for clarification, is the "shield" the trapdoor or the normal, vertical door?))
For clarification: the door to the cellar is angled at forty-five degrees. i called it a trap door, but it is really more of a large, wooden door that swings open to one side. Why they didn't put a double door in instead, i don't know. but that would have been easier to open - each side would have been lighter and all that. So, it's a six foot by four foot slab of wood. Functional, but not pretty or convenient.
You wake up screaming as several of the largest spiders begin tearing into your flesh. You must have the opposite of Arileth's luck. If you don't get help soon, well ...