The Moonstone Twin (level 47)
DISCLAIMER: Your Steps and Tasks may be different
Characters that were created after Patch Version 1.79 do not receive this Epic quest.
Next Brigit sends you to kill a banshee named Rioldna who roams in the water northwest of Alainn Binn. After you kill her and get the first stone, the Faerie Queen appears momentarily and sends you to the healer in Alainn Binn (Ceri), who says you must kill the Faerie Queen in Cursed Forest (night only, east side of the river at 50k/25k). Kill the three maidens to get the Queen to spawn. Kill her maidens first, then kill her to get the second stone. Before she dies, she sends you to free the steed that is being held captive by the far dorochas.
To Find Banshee Rioldna, head to Alainn Binn in far South-East corner of Bog of Cullen and go West-SouthWest to /loc= 44200,52400
I believe it is a night time only spawn. Mentioned in another posting is midnight - 6:00am, I found her at 2:30am
Once you see the apparition of the Faerie Queen, head back into Alainn Binn the north hut and see the healer Ceri.
Target Healer Ceri and type "/say Apparition" and then "/say Faerie Queen".