Xerxes' Webway Stone

{p/u} This amulet has 3 charges per day. An additional charge can be added by spending 10 minutes performing a ritual over a sleeping humanoid who is having a nightmare. At the end of this ritual the nightmare is captured in the stone, adding another charge, even if it would normally be full. By expending 1 charge, the owner can cast Misty Step without expending a spell slot.
The pulsing stone seems to crackle in your hand. Once it belonged to Xerxes, but now? Now it's yours. And the whole Webway wi