So, in my homebrew Eberron campaign, one of my players is a warforged battle smith. He has a half-abberant dragonmark half-Mark of Making, which he inherited from the House Cannith artificer that created him in Cyre right before the Mourning, and tried to transfer his consciousness into the warforged's mind. Long story short, the Mourning warped the process, trapping Gerrith d'Cannith (the House Cannith artificer) inside the dream-scape of the warforged. The warforged recently has been having dreams, nightmares, which is extremely unusual and impossible for warforged, but it has been happening and this is what has happened recently. (Also, the player doesn't know any of this, he only knows he was created right before the Mourning by Gerrith d'Cannith and a few others, and that he has this strange dragonmark on his arm.)

So, his first dream, he woke up near the Creation Forge where he was created. He was strapped to a leaning back chair (almost like one at the Dentist's), and there was a grayish-yellow mist filling the halls. He got up, and looked around, and found Gerrith d'Cannith's body strapped into the chair next to him, with a dagger in his stomach that was faintly glowing, and said "Zondehr of Tira". He wandered around, past the Creation Forge that was still crackling with energy, into the hallway that leads to the outside world. He found the body of a screaming half-orc noble, Nuntin ir'Lanore. He found the exit, but as he approached, everything turned dark. 

He heard in his mind, "Welcome home," from a creepy chittering voice, "You're with us now, and you will never escape.", the voice continued. His dragonmark started burning, digging into his arm, almost like if liquid metal was poured into his arm, it spread, burning and causing extreme pain to everything it touched. The hallway lit up again, "You're home, Corrupted One, you're home." His dragonmark quickly spread all across his body, causing him to collapse to the ground, then it spread, covering the walls, and seemingly growing out as red-orange tendrils emerged from the floor and walls, grabbing him, and lifting him up. The figure of Gerrith d'Cannith then walked up to him, blood still dripping from his stabbed heart. Gerrith said, "You're here to stay."

Then the dream ended.

What do you think?

In summary, Gerrith is in this dreamspace and wants to take control of his body, but not in a hostile way, more like sharing the body. This dream version of Gerrith is actually a Quori pretending to be Gerrith, forming this nightmare realm of his dreams.

Any suggestions? Eventually the character is going to have to free Gerrith, and will escape into the greater dream realm of Dal Quor. 

What is Dal Quor like? The book doesn't have that big of a description, and if my campaign is going this direction I wanted your input of you have any.

It’s a dream realm, so The Neverending Story meets Monsters Inc, A Nightmare on Elm Street, Alice in Wonderland, plus anything the eff else you could imagine. 

I believe one of Keith Baker’s novels deals with Dal Quor pretty heavily... “The Gates of Night?” Might be worth a look. 

Thanks for the suggestions.