ToME WikiIt is a small level with small rooms surrounded by forest. It contains, as you might expect, only spider-type monsters, the worst of which are Elder Arenaes. They are quite tough and they can summon a lot of Arenaes which can cause critical wounds. Being surrounded can be quite dangerous. Bring lots of healing potions and use them freely (>300 hps can be lost in one turn).
Aside from the healing potions, you absolutely need to be poison resistant. Being stealthy is of great advantage since all arenaes tend to overlook intruders and an extra round of attacks can make all the difference.
Once you have killed all the spiders you can get your reward from Celeborn. It is a potion of augmentation which increases all your stats.
Chatter
BobVin: Some may call it cheating, but I found a shortcut to completing this quest. Tried genociding the spiders, but the quest was uncompleted. Ascended the stairs and descended with a rod of Polymorph. Polymorphed one spider into another type of creature, genocided the other spiders, then killed the polymorphed one. This time I got the "Lothlorien is safer now" message. Interestingly, though, kills due to a Genocide don't seem to count towards my piety score, even though I was praying to Tulkas at the time.
FeathinSilyar: Genociding monsters doesn't really count as a "kill". Thus, it won't give you experience, piety, or count for killing quest monsters like this. It is an easy way out, but does nothing for you other than removing the monsters.