Morgan the trickster was one of the liches in Covenant of J'Lynh. It's said that he was the weakest one of the liches.
Morgan was imprisoned in Thyr Morgan under the Fiend's Lair, in a sealed coffin. Until Arkorow decided no one should be imprisoned like that and let him free.
Morgan later possessed Arkorow few times through Morgan's Tophat until the curse was lifted.
Then The Trickster kidnaped Arepo for some nefarious purpose. The party managed to track him down and destroy (?) him with help of Somnian.