And how can I do it? (Without messing with the actual lines of code if possible)
Chances are if it isn’t a patch in builder or available as a toggle on the item table, you will probably need to code it yourself.
You can adjust the universal devil effect % and assign it to multiple item types, but I do not think there is a pre-made solution for multiple percentages to be stored and assigned.
You’ll need to make it if it is important to you.
From a design standpoint, unsure how this will meaningfully change player behavior. If there is some risk of a backfire, whether that’s 10% or 90%, I am going to assume that it is possible to mess up. Psychologically, I’d assume having a devil effect at all will achieve the effect you want, regardless of its probability.
No. The devil effect is built in and is triggered by a special flag connected to the weapon (BTW that’s the reason why you cannot have a poisoned devil weapon).
You would need to completely overwrite some other procedure (like the previously mentioned poison) and make it a duplicate of the devil effect just with different values. But I don’t know much about changing the ROM code so I can’t help with that.
So the answer is No unless you want to put a really long time into making it.
I didn’t want to comment but now I feel obliged because the guy above is just plain incorrect. It would be extremely easy to make the devil effect percentage based on the weapon being used. You wouldn’t need another effect for it, and even you did, the effect uses an entire byte but only has like 6 entries, so even if you did need to do that it still wouldn’t be an issue.
Now I say this with the caveat that, yes, in order to change the game’s code, you need to change the game’s code, so if the thought of that terrifies you and makes you decide not to do it, well a) it shouldn’t and b) you’re out of luck.
You could very easily add a few lines of code here to branch based on weapon id for different percentages. Ask in #advanced_help on discord if you want to learn how.
Well, time to take some coding lessons.