Armor Trap

it looks like a normal breast plate, but when someone puts it on, poisoned spikes shoot out into the body. The player takes one d4 of slashing damage. They must also make a con saving throw with a DC of 12. On a failed save, the player take 2d6 of poison damage, on a passed save they only take half. 

This armor consists of a fitted metal chest piece worn with supple leather. Although it leaves the legs and arms relatively unprotected, this armor provides good protection for the wearer's vital organs while leaving the wearer relatively unencumbered.