Concealment, spell failure and Miss chance.

[DaRotten]

How does the % roll works?
I assumed that it was like Cthulhu system, if the % is 20, for example, you have to roll 20 or less in a d100.
But aparently im completly wrong, how does exactly work?
You have to roll more than 20?
And in spell failure you have to roll more than what the armor states?
I know that it may sound silly, but just want to be 100% sure. (Get it? 100% sure? haha)

-N

[Lifat]

The standard assumption is that the percentage given is the chance of failure, meaning that you have to roll higher than that on a d100.

In my group I have some superstitious people and I allow them to choose which percentages rolled are failures, such as if they have 20% spell failure then I allow them to say that 80-100 is failed for an example. If they forget to specify before a roll the standard rules (where you have to roller higher than) are used.

[Claxon]

The percentage is the chance that it will fail. So if you have 20% miss chance you have a 20% chance to fail to hit them.

The way this is usually done is to roll a d% die and d10 and add the values together. Usually, before rolling a GM will either ask (or tell you) if the success of railure is high or low (either 81-100 or 1-20).

For spell failure less just take a made of exampel of having 10% spell failure chance. You would choose either 1-10 or 91-100 as your failure range and then roll. As long as you don't roll in the agreed upon range, you succeed.

[claudekennilol]

I like to make it even simpler. If it's a 10% chance of failure I'll roll a d10 and just say "a 1 is failure" likewise if it's 20% I'll say "a 1 or 2 is failure". Of course that doesn't work with odd percentages such as 17% or 61%, but I haven't ever seen those pop up.

But generally yes, you roll a percentile die and a regular d10. Lifat and Claxon have already addressed the main point so I'll just add in that they're correct and it is not like the "Cthulhu system" that you mentioned.

[Jeraa]

claudekennilol wrote:

I like to make it even simpler. If it's a 10% chance of failure I'll roll a d10 and just say "a 1 is failure" likewise if it's 20% I'll say "a 1 or 2 is failure". Of course that doesn't work with odd percentages such as 17% or 61%, but I haven't ever seen those pop up.

Which works fine, but you do have the occasional 5% (or some % ending in 5.) As far as I know, all percentages in the game are multiples of 5. In that case, you could just divide the percentage by 5, then roll greater than that number on 1d20.

So if you have a 20% miss chance, you need to roll greater than (20/5=4) 4. A 50% chance you must roll greater than a (50/5=10) 10.

[claudekennilol]

Jeraa wrote:

claudekennilol wrote:

I like to make it even simpler. If it's a 10% chance of failure I'll roll a d10 and just say "a 1 is failure" likewise if it's 20% I'll say "a 1 or 2 is failure". Of course that doesn't work with odd percentages such as 17% or 61%, but I haven't ever seen those pop up.

Which works fine, but you do have the occasional 5% (or some % ending in 5.) As far as I know, all percentages in the game are multiples of 5. In that case, you could just divide the percentage by 5, then roll greater than that number on 1d20.

So if you have a 20% miss chance, you need to roll greater than (20/5=4) 4. A 50% chance you must roll greater than a (50/5=10) 10.

I do that, too. Most of the time percentiles just aren't needed. Though for 50/50 I usually just grab a die (not my d3!) and just do odd/even.

[Claxon]

Actually, I agree that the d% and d10 combination dice roll just don't seem to work that well. I feel that you just don't end up rolling a reasonable distribution, though I have no evidence for this it is just a personal feeling.

I much prefer to use a digital roller for percentage rolls or to convert it to something that can be rolled on the d10 or d20.

[Lifat]

Claxon wrote:

Actually, I agree that the d% and d10 combination dice roll just don't seem to work that well. I feel that you just don't end up rolling a reasonable distribution, though I have no evidence for this it is just a personal feeling.

I much prefer to use a digital roller for percentage rolls or to convert it to something that can be rolled on the d10 or d20.

I'm pretty sure the reason you feel that there is some sort of bias is 1 of 3 reasons:

1. Defective dice
2. A small sample size that is skewed (but will even out on a larger sample)
3. superstition

That said I do feel like the d100 is a carry over from 2nd edition where you actually could get percentages that weren't easily represented with other dice.
If my players want to use other dice then I'm fine with that as long as the percentages actually match up.