Cathulhu was a vastly powerful entity dwelling at the bottom of the ocean awaiting for the stars to be in the correct alignment for it to rise again. This occurs every 60 years, however it appears that Cathulhu requires an outside ritual contained in the Necronomicon to bring this about. It had acolyte creatures known as the "Spawn of Cathulhu" as well as a human cult who worshiped and attempted to awaken it to bring about the apocalypse.
Cathulhu was eventually sent back to the depths when the Ghostbusters used their particle streams to ionize a roller coaster track in Coney Island, causing lighting to strike it, effectively sending 100 Giga Volts of electricity though it. This was however not enough to cause any lasting injury, but was enough to return it to a dormant state, until the stars are right again.
Ghostbusters: The Board GameEdit
Ghost Card InformationEdit
- To Hit: 3 or higher
- To Trap: Cathulhu cannot be trapped.
- When Hit: Move 2 spaces towards that Ghostbuster.
- When Missed: Moves 2 spaces towards that Ghostbuster, them moves 1 space in a random direction.
- (Set-Up) Cathulhu starts with 3 Slime tokens on it.
- Terrain and Ghosts do not block Line of Sight to Cathulhu.
- When Cathulhu is adjacent to a Gate as it closes, remove a Slime token. When Cathulhu has no Slime tokens, remove it from the scenario and each Ghostbuster gains 3 XP.
- At the end of each Ghostbuster's turn, Cathulhu moves 1 space towards the nearest map edge. If Cathulhu leaves the map, you lose the game.
- Push - When Cathulhu moves into a Ghostbuster's space, they get Slimed and are moved 1 space in the same direction.
Cathulhu is one of the "Old Ones," which are a race of extra-dimensional beings who once ruled Earth, but has since been banished by unknown means for unknown reasons. Cathulhu has since dwelled at the bottom of the ocean, and every 60 years the stars are in correct alignment to rise again.
According to Egon Spengler, Cathulhu makes Gozer look like "Little Mary Sunshine" and is "completely off the scale" in terms of power.   This would indicate that it is well beyond the standard classification system.
In Ghostbusters: The Board Game, Cathulhu is a Class 8.
Cathulhu is capable of physical regeneration, as shown when the Ghostbusters fired their Particle Streams at his head. As a result of this, and its inherent power, it was entirely immune to conventional ghostbusting techniques. It did possess a weakness to magic, however it would take a magician of vast ability to have anything other than a very short term effect on him, as shown when Professor Derleth attempted use an incantation to return it to its slumber.
According to Ray Stantz, H.P Lovecraft used Cathulhu to create works of fiction. This is a reference to the author of many short stories set in the "Cthulhu mythos" written around the 1920s. Such stories included the Necronomicon, and were in fact published by August Derleth, who the Cathulhu expert was obviously named for.
- According to J. Michael Straczynski on Twitter, Cathulhu "Should've been [spelled] Cthulhu, but the stupid title person thought it was a typo missing a vowel and "fixed" it." 
- On page eight of Ghostbusters: Get Real Issue #2, Peter, from The Real Ghostbusters, asks if the Ghostbusters ever encountered Cathulhu. 
- On March 8, 2015, the 22nd stretch goal is Ghostbusters: The Board Game, $1100K, was also revealed: Cathulhu. 
- On March 10, 2015, Cathulhu was unlocked.  The 24th and last stretch goal, $1325K, was later introduced: an upgrade of Cathulhu to 100mm. 
- On March 11, 2015, The Cathulhu 100mm upgrade was unlocked. 
- On Cathulhu's character card in Ghostbusters: The Board Game
- The caption on the photograph quotes Egon's "Its power is completely off the scale!" line from "The Collect Call of Cathulhu"
- The biography mentions the back drop of "The Collect Call of Cathulhu" in which the stars are in correct alignment every 60 years to summon him.
- Erik Burnham considered using Cathulhu as a primary antagonist in Ghostbusters Annual 2018 but ultimately decided on a new version of Samhain, Connla. 
- ↑ Egon Spengler (2009).The Real Ghostbusters- "The Collect Call of Cathulhu" (1987) (DVD ts. 05:48). Time Life Entertainment. Egon says: "Cathulhu."
- ↑ Egon Spengler (2009).The Real Ghostbusters- "The Collect Call of Cathulhu" (1987) (DVD ts. 05:57-06:00). Time Life Entertainment. Egon says: "Cathulhu makes Gozer look like Little Mary Sunshine."
- ↑ Egon Spengler (2009).The Real Ghostbusters- "The Collect Call of Cathulhu" (1987) (DVD ts. 17:25-17:30). Time Life Entertainment. Egon says: "His power is completely off the scale. None of our equipment can begin to stop it."
- ↑ Peter Venkman (2009).The Real Ghostbusters- "The Collect Call of Cathulhu" (1987) (DVD ts. 13:28-13:31). Time Life Entertainment. Peter says: "Anything that looks like Godzilla wearing an octopus hat shouldn't be hard to find."
- ↑ straczynski Tweet 3/4/16
- ↑ Peter Venkman (2015). IDW Comics- "Ghostbusters: Get Real Issue #2" (2015) (Comic p.8). Peter says: "...Cathulhu?"
- ↑ Ghostbusters: The Board Game Update #38 3/8/15 "Bigger is better"
- ↑ Ghostbusters: The Board Game Update #41 3/10/15 "He makes Gozer look like Little Mary Sunshine!"
- ↑ Ghostbusters: The Board Game Update #44 3/10/15 "You can thank him for Halloween..."
- ↑ Ghostbusters: The Board Game Update #46 3/11/15 "Off the scale!"
- ↑ FreakSugar "Erik Burnham on Samhain, "Crossing Over," & All of the Ghostbusters!" 3/21/18