''Cthulhu: An Unspeakable Mod'' is a ''VideoGame/HalfLife1'' GameMod, based on the Franchise/CthulhuMythos. You play as Ranulf Stafford. Ranulf is an occult investigator who has been having bad dreams recently. Dreams of an sunk island resurfacing, and men awakening an evil of propotions no man can comprehend.

So one evening he visits his old friend Sir Henry, only to find a letter from Henry himself, that says that he has gone to his church. Ranulf decides to search for him there, and that is when the journey starts; pulled into the madness that is the knowledge of the Great Olden Ones, and a cult planning to awaken the great Cthulhu. The only one able to stop them, is Ranulf.

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!!''Cthulhu: An Unspeakable Mod'' provides examples of the following tropes:

* AbsurdlySpaciousSewer: The one below the City of Yith.
* AlienGeometries: The City of Yith is full of it.
* ApocalypticLog: Many pages written by cultists, scientists and Henry are found in the mod.
* ArtifactOfDoom: You read the Necronomicon in the library. Immediately afterwards, enemies attack.
* CassandraTruth:[[spoiler: no one believes Ranulf when he returns from R'Lyeh after saving the world, and thus he is locked up in Arkham Asylum.]]
* ChestBurster: A man lying in a bed screams and then die. Then small spiders burst out of his body.
* CosmicHorrorStory
* CorruptChurch: The Black Church. Full of chanting cultists.
* {{Cult}}: The Esoteric Order of Dagon.
* DidYouJustRomanceCthulhu: [[spoiler:Dr Whately gave Yog-sothoth his wife. The small spiders you have been fighting the whole time have been the offspring.]]
* DreamingOfThingsToCome: Ranulf dreams of the Esoteric order awakening Cthulhu before the game starts.
* DrivenToSuicide: Dr. Whately, who created the monsters in Dunwich, is found dead with a knife and a note explaining it.
* EldritchAbomination: Cthulhu and Dagon.
* EldritchLocation:
** The island above R'lyeh.
** You also go Millions of years back in time to the City of Yith.
* EnemyChatter: "''The stars are almost right...''"
* EvilLaugh: One of the cultists does one, [[spoiler: After Ranulf has been locked in the asylum. They are now free to awake Cthulhu again.]]
* ExclusiveEnemyEquipment:
** The Thompson is only gained by picking it up from a dead Mobster later on in the game.
** The cultists are carrying daggers that you can only get by killing them.
* FishPeople: The Deep Ones.
* GameMod
* HumanSacrifice: Ranulf witnesses a man dying being dropped from a cage into a well, filled with acid.
* ImmuneToBullets: The scientists experiments that can only be killed by fire or magic. Also, Cthulhu.
* InvisibleMonsters: the Spawn of Yog-sothoth.
* JumpScare: Most of them in The Ghoul's Lair. The caves are small and narrow with sharp turns, so you might often end up in front of one of the Ghouls.
* JustifiedTutorial: Since most people should already know about moving and firing in a gold source game, the hazard course simply consists of visiting Sir Henry. Then he explains how the powers of the spellbooks work.
* KillItWithFire: Father Dagon, and some other enemies, are weak against fire.
* LaserHallway: Ranulf wanders into one in Yith. Fortunately, there is a grid on the floor that he jumps through, surviving the trap.
* LifeDrain: The Spellbook of the name Drain Life can do just that from human enemies.
* LoadsAndLoadsOfLoading: The maps are smaller than the usual, which means then leaving an area might load again and again. Thankfully, they are still only a few seconds long, as in most Half-Life mods.
* LovecraftCountry
* MolotovCocktail: One of the useful weapons obtained.
* MoreDakka: The Thompson gun gets a lot of ammo while visiting the lair of the Mob.
* NamesToRunAwayFromReallyFast: Every area in the game really. Innsmouth, Dunwich, Ghouls Lair, City of Yith, R'lyeh...
* NewWorkRecycledGraphics: In many places. Most notably in R'lyeh, you encounter Shock Troopers from ''[[VideoGame/HalfLifeOpposingForce Opposing Force]]'' more or less unchanged. They're presumably supposed to be Cthulhu's star spawn. Cthulhu himself, meanwhile, uses a sized-up and modified Gargantua model.
* OccultDetective: Ranulf Stafford.
* OminousFog: Innsmouth is sweept in one.
* OrganicTechnology
* OurGhoulsAreDifferent: The way that leads into their lair might be in a graveyard, but just like the rest of Lovecraft, they are neither demons or undead.
* ParanormalInvestigation
* SanityMeter: Using the magic attacks costs the sanity of Ranulf. When it reaches zero it's game over, and it can only be refilled by defeating the bigger enemies in the mod.
* SpellBook: Weapons which Ranulf hold while casting the different spells.
* SpookySilentLibrary
* StandardFPSGuns: And some not so standard.
* StarfishAliens
* StealthPun: The icon that represents the sanity meter on the hud is a small picture of Howard Philips Lovecraft. You get HP for defeating bosses.
* SwordCane: The first weapon is one, found in Sir Henrys Wisdom church.
* TheBlank: The Night Gaunts. Though it is hard to see since it is so dark in the areas around the Church.
* TheMafia: The Finucciaro family.
* TheRoaringTwenties
* TownWithADarkSecret: Innsmouth.
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