Extended universe sigilLu-Kthu is an Outer God created by James Ambuehl, American horror writer which has contributed to expand Lovecraft's Cthulhu Mythos with the Lu-Kthu Cycle of stories. It is said to be the Birth-womb of the Great Old Ones, described as a "A titanic, planet-sized mass of entrails and internal organs. On closer examination it appears a wet, warty globe, covered with countless ovoid pustules and spider-webbed with a network of long, narrow tunnels. Each pustule bears the larva of a Great Old One".

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