Crysa-Thul

Dead (technically "still-born") fetal deity from pre-stream. Vox Machina reached him via a "Planar rift" located in Stilben.
They originally found him because they were baited by "Fendril Vas", a worshiper of Crysa-Thul who told them he was hiring them to investigate a new business conglomerate called "The Myriad"