Some Magic Items, are not cursed, just.. expensive..

Looking at some of the movies and the artefacts they give us, can influence or create ideas:

StormBreaker: the Cursed Axe

Our Hero, finds this massive axe, finding he has the strength to wield it, he enters battle, and mid fight, when the player rolls a double 12, the GM determines that this "double bad" can mean the discovery of the "curse" of the axe.

The GM asks the player, you know this is bad, so I'll get you to roll a d6, but I'll let you add a number to it of your choice, which will affect the power of this axe. The Player chooses 10, and rolls a 5. 

The Axe flies from his hands, lightning crackles from its metallic sheen, the axe embeds itself into the opponent, taking 225 damage, yet microseconds later, the opponent disintegrates the axe slowed, still continues its arc into the ground, and within a 15ft radius, all creatures take 15 damage, they are mostly killed.

The character though, our hero, is drained by 15 magic points, magic he doesn't fully have, this, according to magic rules, causes some physical damage, and severely hampers his ability to regain magic (the negative modifier cancels out any natural regeneration rate, and % chance to learn)

Stormbreaker is just a regular axe, mostly. It only becomes dangerous when you try to actually channel power through it.

Captain America was able to swing it, when needed, as a plain axe, no lightning going off.

Thor understood that the Axe would drain off power, to cause its effect and thought "their bodies would crumble and their minds collapse" 

Mjolnir, has its own, internal MP to enact its powers, but Stormbreaker conjures lightning bolts and open portals, siphoning off your own power.

If you have no MP to give Stormbreaker, you’d be literally draining your lifeforce (blood magic). Your very natural essence would be drained away, and you would die.

For a god like Thor, or anyone else who has loads of energy stored inside of them, that’s no problem. The weapon would just amplify and project whatever power you normally produce without it.

But for non magic users, it’s very dangerous.

This gives GMs a whole set of 'effects' that create magic items, that act like curses. Draining the life force of a person, causing negative effects, where else have I seen that?

Harry Potter, carrying the Horcrux, he and his companions, magic users at least, were being constantly drained, and an effect of it was a poisonous effect on their mind. Doesn't need to be a 'curse' effect that is laid upon a player, instead its a result of the negative MP score. 

The story might have a magic item, something like a bracelet, that makes the player 'feel more powerful' maybe bestowing a +1 STR value, BUT each time the STR component might be needed, the GM imposes a -1MP modifier, the object is draining the players magic to 'cause' it to work. if the player is not a magic user, the effect is recorded by the GM but the affected hero would feel the results.

any Strength task that is at least half of the STR value of the character, would trigger, minus a MP from them, and slowly, be draining their life as per blood magic rules.

The player would only get informed of the modifier once they reached the -1 effect to their character sheet. Taking the bracelet off won't affect the drain, since the drain is on the character, The player might think they are cursed, go to a shaman or healer, and have the curse lifted. no effect. the player, unaware or unsure, but put the bracelet back on. 

Only if they put the bracelet on a magic user, who then uses their strength to perform an action will notice the subtle change, the MP cost, and realise, the 'cursed' character is actually just magic drained.

The Beauty of this, the players have discovered a negative, they search out the negative, and if they experiment with the bracelet, they'll stumble on the clue and realise what's happened. The MP can be restored with rest & channeling from the mage, the players all learn something about the rules of magic, the players figure it out for themselves, instead of the GM force-feeding them the knowledge, and it can last several sessions, the 'fighter' being "ill" for several sessions, not knowing how / why, but in effect being a whole level worth of stats lower than usual, forcing the group to rethink their game plan for several sessions.