Key to Phantoms' Cloister is an adventure module from the RPGA Legacy of the Green Regent campaign.
The annual haunting of a ghost in the streets of Loudwater is interrupted by a groundling attack. Their burrowing reveals a previously undiscovered reliquary containing a tangible shard of pure light. Following clues, the party makes their way to the ruin of Phantom's Cloister where they find Zhentarim battling creatures under the control of a vicious quasit.
LGR01 Extermination • LGR02 Gray Hunt • LGR03 Key to Phantoms' Cloister • LGR04 Secret of Phantoms' Cloister • LGR05 Dark Exodus • LGR06 Epidemic • LGR07 Nurture and Nature • LGR08 Rat's Bastard • LGR09 Denial of Resource • LGR10 Into the Fallen Lands • LGR11 Humility • LGR12 Tyranny • LGR13 Book Knowledge • LGR14 Native Intelligence • LGR15 Caravan to Waterdeep • LGR16 In Cold Blood • LGR17 Tour of Duty • LGR18 Feast of the Moon • LGR19 A Difference of Opinion • LGR20 The Howling of a Mighty Storm • LGR21 The Truth of Hearts • LGR22 As Seconds Slip Away • LGR23 Strange Bedfellows • LGR24 To Sever the Snake's Head