Throne of Past Lords
Mechanical trap
When anyone who doesn’t press a small indentation on the underside of the right armrest sits on the throne, a poisoned blade thrusts upward beneath his right leg. Those who fail a DC 16 Dexterity check take 28 (8d6) piercing damage and 15 (6d4) poison damage, or half as much damage on a successful one.
A DC 17 Intelligence (Investigation) check reveals the slot in the seat that houses the blade, and a DC 20 check reveals the indentation in the armrest. A DC 15 Dexterity check made with thieves’ tools disables the trap.
Anyone who sits on the throne and survives the blade must succeed on a DC 20 Wisdom saving throw or become possessed by spirits. The character can attempt one DC 15 Charisma (Persuasion) check with disadvantage to communicate with the spirits. The character cannot ask a specific question, but can only channel the spirits to provide one piece of information.
If the sitting PC succeeds on the Wisdom save, she is not possessed. Quite the opposite; she can converse peaceably with the skeletons as though they were under a charm person spell. They take no actions beyond answering questions. During that time, the PC can ask questions and compel answers, making a Charisma (Persuasion) check each minute she controls the undead. If she is a cleric or paladin of a death god, she gains advantage on this check. Of course, the bones know only their side of the story. A creature can only sit on the Throne of Past Lords once every 24 hours.