I killed the PH at the top about 20 times and finally just killed all the way down the ramp through the pit after reading this comment and found Thisla at this exact spot on the next set of spawns. Thank you!
Drops fractured seminal essences. (wrist/hands) The images are pretty weak and fade after like 10 or 20 seconds. I just let cleric merc tank it or either tank can pick em up.
If you drop down the pit, and go up the ramp that spirals, her ph is the roamer that goes up and down the 2nd and 3rd "levels" of the spiral. The first corner with one mob going up is a safe place to camp after you kill the static spawn there. After that just wait for her to path to you.
When we pulled this mob, we were very surprised to find out that it spawns a twin once we started fighting.
[]Thisla, Twinskull Matron shudders as some of her life force flows into her double! Thisla, Twinskull Matron grins as her life force is renewed by her double![/]
We had the monk off tank the twin for awhile and then get the message
[]Thisla, Twinskull Matron dissolves into a mist, which flows back to her original form.[/]
She called her double a couple of times during the fight. She does Flurry.