Y'tossi

Y'tossi will spawn when the Heart Key is turned to unlock the western pedestal in Watcher's Keep Final Seal dungeon.
She is a Tanar'ri demon, appearing as a Marilith.
==Gameplay==
Y'tossi can See the invisible.
She seeks to get into close quarters combat and will move rapidly toward the first enemy seen.
Once she spots an enemy she'll apply her initial spell preparation protections.
She is immune to a number of Status Effects and has a high Magic resistance rating.
When her HP falls below 50% she'll apply a Cure Serious Wounds spell, which can't be disrupted. This can be done again after a timer has expired, if applicable.
If she spots a mage or sorcerer class enemy, and their magic resistance is less than 50%, then a Cloudkill is cast at them.
Party members that are struck by her in melee will notice the heavy physical damage, as well as some random elemental and poison damage effects determined by her special longsword.
Each strike from her sword has a random d100 probability check to determine the extra effects applied to the target:
* 0-10% - Extra 1d6 Fire damage
* 11-20% - Extra 1d6 Acid damage
* 21-30% - Extra 1d6 Cold damage
* 31-40% - Extra 1d6 Electricity damage
* 41-50% - Extra 1d6 Magical damage
* 51-60% - Extra 1d6 Piercing damage
* 61-90% - Poison effect applying 2 Poison damage/s for 5 seconds
* 91-100 - Extra 1d6 Poison damage
All of these effects bypass magic resistance, Power level protection, and have no Saving throw.
Upon death she drops the Gauntlets of Extraordinary Specialization, Rogue Stone, and a random treasure.
==Bugs==
Y'tossi's regeneration ability timing mode is set as permanent, but that setting requires a duration to work, and it has no duration, and therefore it doesn't operate correctly. This is an issue throughout the game in several other creatures as well. This issue is included in The Enhanced Edition Fixpack (EEFP) and is already identified to Beamdog for possible fixing in the future.
==Gallery==
Heart Key Fight 5.png|Y'tossi will animate several skeleton warriors during the fight.
Heart Key Fight 2.png|If the she-demon spots a mage class enemy, she'll release a Cloudkill upon them, polluting the battlefield atmosphere with poison.
==Mod content==
The Sword Coast Stratagems mod will make some revisions to this creature.
Experience level is raised to 20/20/20.
The demon's AI script is improved with more recognition of the enemy's protections and buffs to decide when to cast innate Remove Magic spells when desired.
The creature uses Blade Barrier, aims Cloudkill at some different targets, and will initiate "teleport without error" ability to chase down weak or wounded enemies.