Well, I changed the code to this.
Battle::AbilityEffects::DamageCalcFromTarget.add(:INFLATION,
proc { |ability, user, target, move, mults, baseDmg, type|
mults[:final_damage_multiplier] /= 2 if target.hp > taget.totalhp / 1.5
elsif
mults[:final_damage_multiplier] /= 1.6 if target.hp...