Need help making an item that works off of a stat or lvl

Hello videogame makers! This is my first of hopefully many posts.

Ok, Using RPGM XP, looked aound at other tutorials and couldn't find an answer (although what I need may be there but I just didn't recognise it). I would like to do this without using scripts as I have only had RpgMXP for about a week (hey, got to start somewhere) and have not even looked at scripting yet.

What I want to do for a game I have started is make a consumable item that deals damage based either off the character's level or off their stat (I haven't decided which I like better).

I want to make items that will be usefull thoughout the game. I thought about using the %HP on dealing damage, what if I make an item that hits for 50%HP and use it against a boss? Half thei HP is gone in one hit. Unless someone can tell me how to make a percent item less effective against certain creatures and bosses. That would also be acceptable.

If noone can help me, no worries, I'll just make them less expensive Items and less powerful. Appriciation in advance.

No, I know how to add an element. What I mean is make the the item, (in my game I was thinking cards with magic sealed in them) deal damage based off either Str or Int, depending if it is supposed to be a physical damage dealing card (like summoning a sword) or calling forth a fireball. That way a card would be useful at lvl 1 with 50 Int or lvl 100 with 500 Int. I'm just trying to make it easier than making 5 versions of each card I want to make. I thought about using %HP for damage, but I don;t know if it deals static damage every time.

COMMON EVENTS

I haven't messed with common events yet. I'll have to look up a tut on them.