I suggest stepping back 25 feet from this dais. Unless Sim has a sense from his previous checks that the cold/necrotic is a trap, he will look for the shortest route to the thrown to get in position behind the seat. If something seems like it will happen when he steps on the dais, he will jump back. Otherwise, he will quickly remove one eye gem with his dagger. If nothing happens, he will repeat this for one of the teeth gems. If something does seem like it will happen when he removes a gem, he will try to jump back away from the throne and dais.