Spectral potion

A spectral potion is a potion created during the 2017 Hallowe'en event. It is made by using a murky potion on the Zamorakian altar in the southern part of Varrock. When this is done, a message in the chatbox states You feel a dark power emanating from something in your backpack.

Using it on a masked stranger will trigger a cutscene, resulting in the player supposedly being killed by Jonas and being brought back to life by the Grim Reaper.