Extended universe sigil Yaggdytha (The Incandescent One) is twin brother of Vorvadoss, and first-born of Nodens, the Lord of the Abyss. Yaggadytha is also associated with Bel-Yarnak. It manifests as a great amorphous, incandescent ball of cyan living energy, spread itself into a web of giant talons of light.

It is mentioned in the Book of Iod, The Celaeno Fragments, The Revelations of Glaaki, and an untitled work by Johannes Henricus Pott.

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