I tried to create an effect similar to the arcane rune, so I figured the MODIFIER_PROPERTY_MANACOST_PERCENTAGE modifier function should reduce the mana cost of your spells/items, but instead it seems to do nothing? I seem to be the first person to actually use this function, since github and google came up with no results. Is nobody using it just because it doesn't work? Or maybe it just has some less obvious effect that, I don't know. If somebody used this function successfully in a lua modifier, please respond.