From Lexicanum

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Etrodai is a demonic entity probably in the service of Khorne that orchestrated the invasion of Herodor and ordered the assassination attempt of the newly reincarnated Saint Sabbat. Having recieved orders from his master Enok Innokenti he summoned nine entities to his service  : A triplet of Loxatl, Pater Sin and two mutated psychers, a chaos dreadnought named Karess, an elite sharpshooter of the Blood Pact and a Dark Eldar mandrake named Skarwael. This nine were meant to compete in the destruction of the Saint and be rewarded by Etrodai.

Sources

Gaunt's Ghosts Omnibus "The Saint", by Dan Abnett, BL Publishing