Sir Prysin is a non-player character located on the ground1st floor[UK] of Varrock Castle, in the southwest room. He is the descendent of Wally, the demon slayer of Varrock. He is the current keeper of the legendary sword Silverlight.
In the Demon Slayerquest, he tells the player about the three silverlight keys that are needed to unlock the chest containing Silverlight. He informs the player that Traiborn the wizard has the first key, Captain Rovin has the second, and Sir Prysin himself accidentally dropped the third key down the drain outside the castle's kitchen. After collecting the three keys, the player can return to Sir Prysin to receive Silverlight.