Necrotic Spike (trap idea)
Here's one for you Dm's that want a trap that deals Necrotic damage. The players are passing by a room when they see that there's a medium sized obelisk spike in the room. On the obelisk that carved in symbols on it. The symbols show a person pricking there finger on the obelisks shop tip & then gold coins fall from the ceiling. If any of the players decided to prick there finger on it, they will not get any gold, instead they will take 1d6 +4 necrotic damage. If the players look around after the fact, they will notice that there is a device in the ceiling that would have dropped gold... it just happens to be empty.