It's a deep cave full of Silk Mantises, creatures with sharp blades in their arms and capable of creating silk webs that they use to hunt their preys and store them to feed the hive.

Plot hooks idea

A lot of people is being reported missing, the Silk Mantises are capturing them in their cocoons. Save as many as you can. Kill the Queen and/or the rest of Mantises before they become unstoppable.