Call of Cthulhu D100 Monsters to D&D D20?

[Jestersama]

I'm looking at inserting some Lovecraftian creatures into my D&D adventure. I own a (6th? Ed) Malleus Monstrorum from the Chaosium ruleset.

I don't need the entire rulset, merely guidelInes on how to convert creatures into D&D.

Could anyone help me out with this?

 

[Cleon]

I'm looking at inserting some Lovecraftian creatures into my D&D adventure. I own a (6th? Ed) Malleus Monstrorum from the Chaosium ruleset.

I don't need the entire rulset, merely guidelInes on how to convert creatures into D&D.

Could anyone help me out with this?

Sure. What monsters are you after?

Many of the standard Lovecraft monsters have official conversions in the d20 version of Call of Cthulhu, which basically uses the same monster rules as D&D 3.0., so if you want to use any of the monsters in that source you might as well use the official stats.

The book includes normal monster writeups for the following entities:

Animated Corpse, Servitors of Glaaki, Byakhee, Colour Out of Space, Cthonian, Dark Young of Shub-Niggurath, Deep One, Dhole, Dimensional Shambler, Elder Thing, Fire Vampire, Flying Polyp, Formless Spawn (of Tsathoggua), Ghoul, Gnoph-Keh, Great Race of Yith, Gug, Hound of Tindalos, Hunting Horror, Insect from Shaggai (Shan), Lloigor, Mi-Go (Fungus from Yuggoth), Nightgaunt, Rat-Thing, Serpent People, Servitor of the Outer God, Shoggoth, Shoggoth Lord, Spectral Hunter, Spider of Leng, Star Vampire, Tcho-Tcho, Terror from Beyond, The Worm That Walks.

It also has templates for Chosen of Hastur, Ghost, Loup-Garou and Mummy as well as stats for various animals like sharks and dogs, but they ordinary beasts are basically the same as the D&D versions.

 

[Jestersama]

I haven't decided on which ones specifically, I know I'm going to use the Color Out of Space though. Where would I find the d20 monsters at?

And could I use the differences between the d100 and d20 stats and stuff to possibly come up with a quick and dirty conversion "key" For any not already converted monsters I may want to use?

 

[Cleon]

I haven't decided on which ones specifically, I know I'm going to use the Color Out of Space though. Where would I find the d20 monsters at?

As I said, they're in the d20 Call of Cthulhu hardback which, unfortunately, is long out of print. The book's still available on the secondary market but it's rather pricey, and I don't think there's a cheaper pdf version on sale as a download (at least I couldn't find it on DriveThruRPG.

It'd be easier if I post the d20 stats of a few monsters from the book here.

And could I use the differences between the d100 and d20 stats and stuff to possibly come up with a quick and dirty conversion "key" For any not already converted monsters I may want to use?

There's some monster conversion guidelines in an appendix of the d20 CoC book, but they're pretty basic. The entire entry amounts to:

d20 Speed: equals Chaosium move multiplied by 4.
d20 Hit Dice: equals Chaosium HP divided by 5.
Damage: depends on size:

Size	Bite/Bash Damage	Claw/Tentacle Damage
Fine	1	--
Diminutive	1d2	1
Tiny	1d3	1d2
Small	1d4	1d3
Medium-size	1d6	1d4
Large	1d8	1d6
Huge	2d6	1d8
Gargantuan	2d8	2d6
Colossal	4d6	2d8

Weapon: divide Chaosium % by 10 and add ability modifier to determine attack bonus.
Armor: Give "appropriate" natural armour bonus from +1 to +10 and add damage reduction equal to 3-5 per point of Chaosium armor.
Sanity Loss: same as Chaosium.

 

[Jestersama]

Would you be willing to post a d20 creature stats? While I understand what you posted having something to compare a d100 stat monster to would be extremely helpful.

 

[Cleon]

I haven't decided on which ones specifically, I know I'm going to use the Color Out of Space though. Where would I find the d20 monsters at?

Here's the official d20 Call of Cthulhu stats for the Colour Out of Space. Incidentally the book uses the British "Colour" spelling for its name, which I believe was used in the original short story.

Colour Out of Space
Medium-Size Outsider (Greater Independent Race)
Hit Dice: 10d8 (45 hp)
Initiative: +4 (Dex)
Speed: Fly 75 ft. (perfect)
Armor Class: 14 (+4 Dex)
Attacks: +14/+9 melee touch attack
Damage: Envelop 1d6+ability drain
Face/Reach: 5 ft. by 5 ft./5 ft.
Special Attacks: Ability drain, disintegrate, spell-like abilities
Special Qualities: Incorporeal, vulnerable to ability-draining spells (as long as the ability is not Con, Wis, or Cha), imprisoned by magnetism
Saves: Fort —, Ref + 11, Will —
Abilities: Str 18, Dex 18, Con —, Int 12, Wis— , Cha —
Skills: Cthulhu Mythos +5, Hide +17, Knowledge (any four) +14, Listen +17, Move Silently +17, Spot +17
Feats: Dodge, Stealthy, Alertness
Challenge Rating: 10

I'll give an outline of the Special Attacks:

Ability Drain (Su): drains 1d3 from each of the target's ability scores. If it drains Con to 0 the victim dies immediately, if it drains any other stat to 0 they have a lingering death over 1d6 days. The corpse is a dry gray husk.

Disintegrate (Su): The colour can disintegrate a passage through any substance at a rate of 1 yard per minute, minus 1 inch per point of hardness.

Spell-Like Abilities (Su): At Will—bind energy, cloud memory, contact human, detect life, dominate animal, dominate person, hypnotism, siren's song, soul singing. Some of these SLAs are from the CoC d20 book.

For another d20 take on this monster, there's also an official Pathfinder version of the Colour out of Space in Pathfinder Bestiary 4.

Pathfinder has stats for some other Lovecraft monsters too, including Dholes, Spiders of Leng and Moon Beasts.

 

[Jestersama]

Ah that's great! Thanks so much, man.

 

[Cleon]

Ah that's great! Thanks so much, man.

Glad to oblige.