Cthulhu is a giant being, one of the Great Old Ones in H.P. Lovecraft's Cthulhu Mythos. It is often cited for the extreme descriptions given of its appearance, size, and the abject terror that it invokes. Because of this reputation, Cthulhu is often referred to in science fiction and fantasy circles as a tongue-in-cheek shorthand for extreme horror or evil.
The deck contains the usual 22 Major Arcana cards, and four suits of 14 cards, plus two extra cards with a listing of the symbolism of the suits and Major Arcana cards:
MAJOR ARCANA CARDS
0 Fool - Azothoth (Air)
I Magician - Nyarlathotep (Mercury)
II High Priestess - Bast (Moon)
III Empress - Shug-Niggurath (Venus)
IV Emperor - Amun (Aries)
V Hierophant - Dagon (Taurus)
VI Lovers - Deep One & Bride (Gemini)
VII Chariot - Beast of Babylon (Cancer)
VIII Strength - Shoggoth (Leo)
IX Hermit - I'thakuah (Virog)
X Wheel - Yog Sothoth (Jupiter)
XI Justice - Spawn in Sphere (Libra)
XII Hanged Man - Well of the Seraph (Water)
XIII Death - Tsathoggua (Scorpio)
XIV Temperance - Reanimators (Sagittarius)
XV Devil - Cthulhu (Capricorn)
XVI Tower - Great Ziggurat (Mars)
XVII Star - Ishtar (Aquarius)
XVIII Moon - Hounds of Leng (Pisces)
XIX Sun - The Empty Space (Sun)
XX Judgement - Guardian of Eden (Fire)
XXI World - Yig (Saturn)
The four suits are called the traditional Swords, Cups, Wands, and Disks, each represented by distinct clusters of gothically designed Court characters and colors.
Cthulhu has also been spelled as Tulu, Clulu, Clooloo, Cighulu, Cathulu, Kutulu, Q'thulu, Ktulu, Kthulhut, Kulhu, Thu Thu Hmong, and in many other ways. It is often preceded by the epithet Great, Dead, or Dread.
Lovecraft transcribed the pronunciation of Cthulhu as "Khlûl'hloo" S. T. Joshi points out, however, that Lovecraft gave several differing pronunciations on different occasions. According to Lovecraft, this is merely the closest that the human vocal apparatus can come to reproducing the syllables of an alien language. Long after Lovecraft's death, the pronunciation "Kathoolhoo" became common, and the game Call of Cthulhu endorsed it.
Cthulhu first appeared in the short story "The Call of Cthulhu" (1928)—though it makes minor appearances in a few other Lovecraft works. August Derleth used the creature's name to identify the system of lore employed by Lovecraft and his literary successors, the Cthulhu Mythos.