For example can we make it so that a character who has high mastery receives a 20% attack boost with that type of weapon?
Low mastery, -20%
I think that's how it works in Disgaea
Sorry for late reply and that exact value of 20% depends on how you setup your game.
You can have it grant +20% of the character's stat but the value added are fixed unless you use evaluate-able string.
ok thank you!