The tower is on this side of the mirror...as are 'we'. Or we were. Now our mirror-selves corpses are scattered about. The red woman did, in fact, kill us.
Yin and her 'sister', Yang, were once one being known as a mirror monster. They were empowered and split to serve as the guardian. Yin is mostly curious about people and would like to be at peace with them. Yang, however, retained the love of murder, and is likely powerful enough to slay us all in a straight fight.
She is also becoming impatient. Yin managed to intercept Kol and Aileph, but their being here means Yang is ready to 'play'.
I tried to convince Yang to leave the kid gloves on, but she 'prefers to break her toys'. Make the guardian half maniacal murder-child, and half blinkered innocent. Wonderful idea.
In the end, we settled on a 'game'. Yang will spend three days and nights hunting us through the mirror side of the city. If we survived that long, she will agree to open the tower door. She will do her best to kill us. This is complicated for several reasons. One, half the city belongs to her outright. Two, she needs no rest. Three, she knows the location of anyone in the city, even in Yin's territory. Note to self: Try to avoid fighting beings on their own demesne next time...
So we ran. Kol's sharp eyes are the only reason we lived: he saw the doors. Each day, one door in the city was white, with a black dot marked upon it. Yin's room, where she got her turn with the 'toys'. We acted out parts of books she liked. One called 'Through the Looking-Glass', mostly. More amusingly, the paladin summoned his celestial steed...to play a part we were missing...
I'm no expert on horse expressions, but I doubt he was amused.
So it went. Each day, we found the door, did whatever Yin wanted to do, then sleep. Yang would then serve as our murderous wake-up call. This only worked in her favor on the third day...days one and two, we had enough warning to run for it, but the third day she kicked in the door. It hit me in the face. I did try fighting her, but my shots didn't really do anything.
Finally, we got though it. Yin and Yang opened the door, and in we went.
The door closed behind us, we went down on the moving platform...and at the bottom, the paladin cast his gaze on me. My own magic senses told me he had done so, right before he started yelling...
“I was right! Explain yourself, warlock. Now.”
“Well. I haven't actually done anything evil, so I'm not sure what you see. But suffice it to say I'm on your side.”
That got him thinking. And checking that headpiece thing. He said lately it could inform you what your patron deity would think of a given course of action. Eventually, he did make up his mind...
“Helm is a patient god. For as long as you're on our side, I will say nothing of it. Transgress, and I will smite you.”
“Fine. Let's get moving...”
Of course, that wasn't the last surprise of the day. That would be the girl who came in after us, claiming to have talked Yang into letting her pass.
I don't believe it...But she's a half-celestial, and a nauseatingly innocent example of the breed, at that. But she wants the chance to heal others, and we're likely to need the help.
The moment the paladin finds out about whatever happened to me, a half-celestial shows up.