Spirit derives from The Iron Wastes, Layer 23 of the Abyss in the Forgotten Realms.
Nilith is one of the Mariliths(an elemental type of powerful tanar'ri fiend). The Mariliths served as tacticians of Abyssal hordes, advisors to demonic nobility, and in some cases acted as serpentine demon queens.
From the waist up, mariliths appeared to be attractive humanoid women with six arms, but their lower halves were those of giant, green snakes. In each hand they carried highly decorated weapons, and adorned themselves with bangles and jewelry.
Forbiddens are very aggressive that can attack everything - including summoner and allies.
Summoning ingredients requires: Demon's Eye, Antarctica Hair Grass, and Icosahedron -