Lienna is a minor NPC in the Mask of the Betrayer campaign.
Mulsantir[]
When you exit the initial barrow, Safiya says that Lienna, a stage director in Mulsantir, can answer your questions. When you arrive at the Veil Theater, it is under attack by Thayan wizards and 20th level Gnolls. Really.
In the back room you find a portal to Shadow Mulsantir, where Khai Kmun has killed Lienna. He says that Araman, his mentor, has staged a coup against Nefris and her allies. He attacks and dies.
Founder[]
Later on you learn that Lienna is connected to the Founder.