@SubRosa - maybe the matriarch is wearing a mask, but it can't be retrieved. Then again, judging from the looks of her arms, it might not be a mask.
The Asylum was very creepy, because for a while Souissi was hunted by a demonic entity that couldn't be killed, it'd resurrect immediately.
Very long story short, Mara enlightened Souissi so now she knows that...
...the Prince isn't his own self anymore, years ago a demon took over and now strives to take over the Reach. With this new knowledge in mind,
Souissi met Prince Damian and his bodyguard Predothor, the tallest man in the Reach, and agreed to have a
dinner with them and some others nobles of High Rock.
Souissi didn't agree with the prince's view of how to gain control over Eastern High Rock by spilling more blood, so she was thrown in a pit and forced
to fight against Predothor. ***
However, when wounded, Predothor, just like his superior, turned out to be everything
but a human being. He was in fact an
Alpha Xivilai.
When Souissi defeated his form on the Nirn, both of them were brought before
the Dagonite Overlord and forced to
fight again for his amusement.
Once again,
the mortal and the Xivilai clashed.
The battle lasted for many hours...
...and once again
Souissi prevailed.
Victorious,
Souissi could now leave the plane of Oblivion and face the Prince.
_____
*** - it's also possible to side with the Prince, in which case you don't need to fight Predothor, instead a new questline opens up. Obviously by disagreeing with the Prince those quests now won't be available to Souissi.
Predothor has been up to now the most dangerous enemy she faced. The battle in fact lasted for many in-game hours. First we needed to figure out how to stop his health from regenerating, once we figured that out, the battle became slightly easier but because of his large pool of health and deadly blows, he was still a fearsome foe. At least the Overlord rewarded Souissi with the "Summon Predothor" spell, so now she can summon the alpha xivilai.