Spider Webs
From City of Heroes: Rebirth - Wiki
Overview
Spider Webs appear on some Arachnoid cave maps. They are not directly targettable by player characters; however, pets and NPC allies may target and destroy spider webs, and player characters may target and destroy spider webs by autoassisting an NPC and targetting through them. If a character passes within melee range of spider webs, he or she will be will be subject to the following effect:
Entangle Point Blank Area of Effect, Foe Immobilize, -Speed
The spider webs can entangle their foes.
