Access to the closet is through a closed pocket door.
|The pocket door is spring loaded to close on the target against the door frame, which has a hidden blade.
A DC 12 Wisdom (Perception) check reveals a small seam in the doorframe that runs the height of the inside frame and along the bottom of the frame.
A DC 12 Intelligence (Investigation) check on the seam shows that the side door frame is concealing a floor to ceiling blade, the bottom seam seems to conceal wire.
If the door is opened, a click will be heard as it locks open. If not noticed, a DC 14 Wisdom (Perception) check will reveal that the wire has risen out of the floor to a height of about 6 inches.
If this wire is tripped, the door slams shut as the blade protrudes from the doorframe. The target must make a DC 14 Dexterity saving throw or take 3d6 slashing damage.
The wire can be avoided with a DC 2 Dexterity (Acrobatics) check.
The wire can also be cut. It requires a DC 12 Dexterity check with thieves’ tools. Failure sets off the trap. If the wire is exposed and above the floor, this check has advantage.