The strange casket is a casket found upstairs in Watson's house in Hosidius. Players must speak to it in order to enable the chance of a reward casket turning into the Mimic.
If players have a Mimic in their inventory, they can bring it to the strange casket to fight The Mimic.
Should the player die in the fight, the strange casket will hold the player's items and will return them for a fee of 90,000 coins (which can be taken from its own storage). Like other Item Retrieval Services, any items stored with the strange casket will be lost should the player die in any unsafe death.