The Architect of Flesh is a major Horror that exists in the deepest depths of the ancient Dwarf Kingdom of Scytha. It considers itself an artist, using flesh as it’s medium and reveling the pain and fear of both it’s victims and those that view it’s work. It has created countless other Horrors, having spent centuries experimenting on the surviving races in the depths of Scytha.
The Passion’s Champions encountered the Architect when the ventured into Scytha looking for the Army of Scytha. They fought it’s twisted creations and made their way past dozens of it’s “artworks” before finally finding the lost palace. Brimmel inadvertently (or perhaps intentionally) invited it to journey to the surface world, as it had been previously unaware that creatures dwelled up there at all.
The Architect is, obviously, a Daelkyr from the Eberron universe. It has the same propensity towards shaping and reshaping flesh, and the same appearance as well. Reading over the description of the Daelkyr in the Eberron book was what made the connection in my brain between Horrors and the Aberration-type creatures in D&D, and gave me tons more fodder for creating interesting Horrors.