Ghost of a Tale

If you have the Trap Master skill unlocked from Rolo, you will be able to re-arm traps, making this even easier.

There's only 5 spiders to kill. 2 in the upper catacombs and 3 in the lower. Stocking up on pine cones and bottles will make this much easier. Try to bring at least 5 bottles when going to kill all of them.

Upper catacombs:

The two in this area are very close together, on the bridge leading up the the middle area, connecting to Dunlain's tomb. One can be easily killed by luring it to a nearby trap (be careful not to spring it yourself). The other one will be easier to kill later.

Quicksave before killing the spiders in the lower catacombs.

Lower catacombs:

You won't be able to access this area until you meet Ravik the Magpie as part of the main story. Once you do get down here, the 3 spiders are all in the same room. In addition, there are 5 pine cones lying on top of coffins in this room and there's also one trap in the room. Lure one spider into the trap and then pick up the pine cones. Now, in my experience, sometimes the spiders health didn't go down even if I threw a pine cone at it. One way to work around this is to throw one pine cone at one spider and then immediately throw another one at the second one. Then try to lure them so they are touching each other. Hopefully, they will both burn each other and their health will go down really quickly.

Ideally, you should have at least one pine cone left for the last one back at the upper catacombs. So just throw it at this one and if need be, throw a bunch of bottles at it.