Has anyone done any work converting Cthulhu Invictus to work with the D20 rules? My players are all accustomed to D&D, and I really like the D20 CoC rules, but I would like to run the Invictus setting. Does anyone foresee any major problems in attempting this?
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I don't see why you couldn't make the transition.Originally Posted by arjomanes
1) Were I to attempt the transition, I would list out the weapons in the Cthulhu Invictus source book, and I would then find the corresponding entries in the D and D 3d edition book to fill up the statistics--if you wish to have an eye to historical accuracy, those are the weapons available and no other in the D and D list.
2) Some attention would be wanted for the problem of armor class, but I am not familiar enough with 3d edition D and D to speak to that--the BRP Call of Cthulhu and Cthulhu Invictus sourcebook leave it that most monsters with any armor at all have enough armor to absorb the rolled damage of most of the culturally appropriate weapons available to Roman adventurers, leaving only the damage bonus. There are a couple of things suitable to barbarians of a Germanic or Dacian persuasion that can do more.
3) Also going over the D and D price list and dovetailing it to the Roman monetary system would be helpful, I think. The Roman prices are predominantly in silver coin, and a gold aureus is a rare and wonderful thing, mainly a money of account, though they do exist. On the other hand, the D and D system focuses on more gold being available in the game, so I think some careful attention to the price list is wanted. The Invictus price list could for that matter do with some expansion.
4) Armor class will want some attention--the heavier forms of plate armors are mostly unavailable. Lorica, to be sure would afford excellent protection, but it is available mainly to soldiers. You have to decide if a private citizen could easily get ahold of it.
5) Good stories are readily available--look for the Falco novels of Lindsey Davis, the Roma sub Rosa novels of Steven Saylor and the histories of Suetonius, Tacitus and Cassius Dio, and also any archaeological news going. The last volume of the Loeb Classical Editions translation of Livy consists of a set of prodigious events, "The Prodigies of Julius Obsequens." Lovecraft once described the Romans as extremely reasonable, and they are, except, of course, when they are not.
That should be enough to get you started.
There's a few books on d20 fantasy Rome floating around (Green Ronin probably still has pdfs of theirs available).
If your players are really familiar with D&D—as in, memorized it—then you should probably have a cheat sheet of differences between the CoCd20 rules and regular D&D, like no AoO, the 10 point MDT, etc.
I think, given what Taterdemalion King points out, that a good approach would be to begin with a good d20 book on Rome, and then port in both d20 CoC rules as needed, and the monsters from there, and the information in Invictus that can be gleaned. That would save much time.
It would also allow the Keeper to insert swords and sandals and other tales as well as Mythos ones, perhaps with more ease.
And Sanity! It is trivially easy to add these modules to nearly any d20 game. The only big difference between CoC d20 and other treatments is the spellcasting mechanic.
Happy is the tomb where no wizard hath lain, and happy the town at night whose wizards are all ashes.
-Ibn Schacabao
You can reverse-engineer in CoC style magic in regular D20 games using the Incantations rules by referencing the suggested spell type/level list in the back of the CoCd20 book.
Sanity got OGLed too, strangely enough.
True, although regular d20 magic doesn't cause ability drain.
I don't think it was strange, just premeditated.
Happy is the tomb where no wizard hath lain, and happy the town at night whose wizards are all ashes.
-Ibn Schacabao
I suspect the ability drain was there to provide an alternative limitation on the frequency of spellcasting. Maybe the spell points variant could be adapted to require temporary WIS or CON damage to provide the point cost?
Thank you for all your replies. That makes me feel better about running the game using this system. Thanks for the references Wombat1; they'll give me a lot to look into.
I do own the Green Ronin Eternal Rome supplement, and I do like much of it. I also purchased their Trojan, Testament, and Egyptian pdfs, which I may use where appropriate. I also own the TSR Glory of Rome book, which may also help, though I haven't read through it in years.
The comments on the combat system are good to take note of. I won't be using a grid, and will be revising the combat rules to follow suit. I think it would take a better Keeper than I to maintain suspense or horror while moving minis around on a battlemat. I also think combatants will only get a free attack if someone turns and runs or uses a spell or bow in melee combat.
I really like the D20 CoC magic system, and I agree its system would work really well in a D&D low-magic setting. Other recent D&D-based games like Dungeon Crawl Classics and Lamentations of the Flame Princess are also doing interesting things with magic. Magic is something that profoundly disrupts the world, and I think often players very familiar with D&D don't see magic as something chaotic and reality-shattering. People of the Iron Age believed in gods and magic and miracles to an extent, but they didn't just sling magic missiles around.
Very kind of you to say.
Magic is part of the furniture in Call of Cthulhu, though usually in the context of something that belabors the investigators. In BRP/CoC, magic is often corrupting, and always a drain on power, I think, so some mechanism might well be wanted for d20, which of course follows more traditional D and D lines. Perhaps a new (new to d20) 3d6 stat, POW could be ported over, which furnishes magic points--use them all and you fall unconscious until one regenerates and 5x which furnishes a SAN characteristic. One could simply bring those two mechanisms over from BRP.
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