Despite his attitude, you decide to try and find the demon's name.
You open the book to a random page, and the strange words from before are still there, utterly indecipherable. They look nothing like any language you've seen, and definitely unlike any you can actually read.
You look up at the mirror demon who is looking at you hopefully. "Go on," he says. "Give it a try."
You flip through the pages looking for some kind of sign, all while acutely aware that the mirror demon is watching.
Eventually, you come across some symbols that begin glowing yellow in your vision. The alien script shifts and changes into something recognizable as:
H E B D E K I E L
You try to say the word, and to your surprise, it leaves your lips in a voice that is not your own. The deep voice resonates throughout the tunnel, cracking some of the mirrors. The Mirror Demon's mirror fractures slightly, but remains whole. When the word is over, you feel suddenly exhausted.
"Hebdekiel," he says. He leans against the side of his glass prison and slides down to the floor. "Hebdekiel. That was my name."
The Mirror Demon stares at you, eyes wide and shining with barely suppressed tears. "Oh wow," he says, his voice faint. "I forgot-- that feels-- wow. Haha. . ." He coughs and tries to compose himself. "I forgot what it felt like."
Parts of his skin begin to crack, as though he's not made of flesh, but plaster. You point at his chest. It's still hollow, but now fresh blood is beginning to seep from the wound. He looks down and appears only mildly concerned.
"Yeah, I see. I, uh, haven't exactly done this before, but I think that'll happen until I get a heart. A heart. A heart!" He suddenly shouts, elated. He scrambles to his feet. "My heart! I know where mine's at! It's in the chamber of the Dead King! Old Skelly Face. I remember!" The joy slowly fades. "I remember. The one who put it there thought it was funny. Because it's so close, but I can't reach it. Can you?" he says. "Can you bring me my heart?"
Before you can do anything, Hebdekial suddenly waves his hands. "Wait, wait, wait. I promised you, didn't I? About your name. Who stole it, probably. The queen of snakes," he says. "Angels can do it, but they've all been diminished like me. Dragons can do it, but the only one around hasn't left his cave in centuries. The only one who might've done it is the Queen. Go find her temple in the desert above."
How the hell are you supposed to do that? You mouth the word how?
"Get bitten by the tunnel snake," Hebdekial says. "He lives up ahead, usually. You'll die for a bit, but you should be fine. So? Will you do it? Will you give me my heart?"
-->[Find his heart?]
-->[Leave him.]