DCs for Mythos Skill checks?

[jhmcmullen]

Note that I also posted this to Monte Cook's board, in hopes of attracting his attention--but I'm interested in how anybody does this.

Okay. This has been touched on elsewhere (problems with d20 thread, whether you use -1 sanity per rank of Mythos knowledge of -5) but I'm going to bring it up explicitly here because I don't find where it has been discussed in exactly this way. (If this has been discussed extensively and a consensus reached, please point me there, and I apologize for wasting your time.)

What difficulties do you use for Mythos skill checks? Bear in mind that the rulebook has no examples and no guidelines about when one uses Mythos skill anyway. The implication is that the difficulties for the Mythos skill are on the same 1-30 scale as other skills. (But Mythos skill isn't like other skills! That's why we need more guidance! :0 )

BRP uses a d% for skill difficulties, where the player rolls under the value (some modification by the Keeper is allowed...+10% or -10%, for example). d20 uses a d20 scale where the player rolls over a difficulty value, usually rated from 1-30.

In keeping with this, the ranks of Mythos knowledge granted by tomes are approximately 1/5th of the ranks granted by those tomes in the BRP version of the game. This makes sense; a d20 has 1/5th the number of probable outcomes as a d%.

The mechanical equivalent of "roll under" in d20 is to set the difficulty value at 20--that is, it provides approximately the same probabilities of success. To preserve the feel for the mythos knowledge being hard to gain and use, a simple solution would be to arbitrarily set the DC for Mythos skill checks at 20.

Except: There is no limit to the number of ranks of Mythos Skill a character can get.

A character can have 30 ranks of Mythos knowledge. (Sure, his or her maximum Sanity is now 70, but that's not much of an impediment. Maximum Sanity has not been significant in my BRP games and I don't expect it to be significant in my d20 games. It simply means that after a certain point characters may not see an improvement in Sanity when they level up. Though by the time a BRP character has the equivalent of 30 ranks of Mythos knowledge, he or she has been a screaming lunatic for a while: 99 Sanity - (30 ranks * 5) = -51 SAN.)

I am trying to reconcile these two things: standard difficulty levels versus no limit to the amount of Mythos skill.

The options, as I see them, are to set DCs differently than for other skills, or to cap Mythos skill at some point.

What do other people do? Does it simply not happen that characters get 15-30 ranks of Mythos knowledge?

Or do you use skill difficulties in a 1-100 range?

I am currently planning on house-ruling this, so that a character cannot have more than a certain number of ranks of Mythos skill, though I have yet to decide on the limit -- perhaps 25, which will give even the most powerful Mythos sorceror a chance not to know something obscure (DC 30, roll of 1-4); or perhaps the character's Intelligence score.

I am also planning to make Mythos skill the appropriate skill for Mythos spells, rather than Spellcraft, which will work for non-Mythos magic.

[phobia]

Well, you have 2 choices.

1) is to keep it consistant with BRP. Max Mythos Skill would be 19. At that level a charater's maximum sanity would be 5.

If you ever achive Mythos of 20, you go insane and become an NPC...

The DC would always be set to 20 for this method. It would reproduce, faithfully, the BRP way of doing it.

2) Keep it consistant with the D20 way of doing stuff. That is, making 29 the max and having variable DCs. You could then use a Mythos multiplier of 3.3 (rounding all results up) to determine max sanity. At 29 your max sanity is 4.

If you ever achive Mythos of 30, you go insane and become an NPC...

The DC would NOT always be set to 20 for this method. It would allow more variation in determining the chance of success.

---

I already feel free in BRP to apply modfiers as needed to any skill check I want, including Cthulhu Mythos. If a character asks about something mythos related and i decide there is NO WAY he could know it, i will reduce his skill to 0%. If he just read "the little golden book of Ghouls" and is now an expert, I might allow a +50% bonus if his question is in regards to ghouls... This is the same techique used to make other tasks more or less difficult using similar justifications...

And, Maximum Sanity DOES come into play... just not too often. I don't know a whole lot about D20 cthulhu but I'll bet in any campaign I ran the players' characters wouldn't stand much of a chance of surviving so long that their Mythos skill ever gets to 95% or above.

[KenFinlayson]

What difficulties do you use for Mythos skill checks?

I use the standard d20 scale of 1-30 (or 1-40 in extreme situations). I use varying DCs for Cthulhu Mythos checks, just as I would for any other skill. Some things are easier than others. Identifying an Elder Sign might be DC 5, while knowing the secret name of Ithaqua used in ceremonies performed by a certain degenerate Eskimo tribe might be DC 30.

Except: There is no limit to the number of ranks of Mythos Skill a character can get.

Rather, I believe that there is no level-based limit to the number of ranks. This distinction is (to me) important. A 3rd level character cannot have more than 6 ranks in a core skill, and no more than 3 in a non-core skill. But that same character could have more than 6 ranks in Cthulhu Mythos, even though CM would not be a core skill for the character.

A limit imposed by Sanity loss would still apply. In effect, no player character could have more than 19 ranks in CM (if we use the +1 rank = -5 Sanity points rule), but they could reach that maximum rank at any level. An NPC madman or creature could have any number of ranks in Cthulhu Mythos, but there would always be things unknown even to them. (This is a nod to BRP, in which even the gods' 100% CM does not guarantee total comprehension.)

[jhmcmullen]

And, Maximum Sanity DOES come into play... just not too often. I don't know a whole lot about D20 cthulhu but I'll bet in any campaign I ran the players' characters wouldn't stand much of a chance of surviving so long that their Mythos skill ever gets to 95% or above.

We generally have no chance of surviving to get to 95%....

[jhmcmullen]

I use the standard d20 scale of 1-30 (or 1-40 in extreme situations). I use varying DCs for Cthulhu Mythos checks, just as I would for any other skill. Some things are easier than others. Identifying an Elder Sign might be DC 5, while knowing the secret name of Ithaqua used in ceremonies performed by a certain degenerate Eskimo tribe might be DC 30.

I thought they were Esquimaux.

Except: There is no limit to the number of ranks of Mythos Skill a character can get.

Rather, I believe that there is no level-based limit to the number of ranks. This distinction is (to me) important. A 3rd level character cannot have more than 6 ranks in a core skill, and no more than 3 in a non-core skill. But that same character could have more than 6 ranks in Cthulhu Mythos, even though CM would not be a core skill for the character.

This is a distinction I was thinking of making, but decided it was implied in the option to set a limit anyway. I wonder if one of the minor typos in the book is that the "no limit" thing should refer to level-based limits.

I have to say that your solution is the closest in spirit to what I want to do. Still not official, of course, but I think it will be workable.

[Keziah]

1) is to keep it consistant with BRP. Max Mythos Skill would be 19. At that level a charater's maximum sanity would be 5.

If you ever achive Mythos of 20, you go insane and become an NPC...

That depends on your rules for max. sanity... we play that it's only -1 for each rank in CM, so 20 ranks still leaves a character playable (thankfully).

As for DC, I think that should be very much task dependent. Something like recognising a distortion of the name of a Great Old One, for example, should have a fairly low DC.