Net Trap

From Xanathar's Guide to Everything, page 113.

Simple trap (level 1-4, dangerous threat)

Goblins, with their propensity to enslave their enemies, prefer traps that leave intruders intact so the victims can be put to work in the mines or elsewhere.


 * Trigger: A trip wire strung across a hallway is rigged to a large net. If the trip wire is broken, the net falls on intruders. An iron bell is also rigged to the trip wire. It rings when the trap activates, alerting nearby guards.
 * Effect: A net covering a 10-foot-by-10-foot area centered on the trip wire falls to the floor as a bell rings. Any creature fully within this area must succeed on a DC 15 Dexterity saving throw or be restrained. A creature can use its action to make a DC 10 Strength check to try to free itself or another creature in the net. Dealing 5 slashing damage to the net (AC 10, 20 hp) also frees a creature without harming the creature.
 * Countermeasures: A successful DC 15 Wisdom (Perception) check reveals the trip wire and the net. A successful DC 15 Dexterity check using thieves' tools disables the trip wire without causing the net to drop or the bell to ring; failing the check causes the trap to activate.