Replace random cards in opponent's hand with Cursed cards form your hand.
If it really is just completely wrecking the entire opponents hand if you only have a Searing Fire or Blood Shrine, then that's kinda overpowered and should be a rare card with cost above 30; consider how dangerous Balrog and Cerebus already are, and this would be worse.
If it's just copying your Cursed cards to your opponent's hand 1-to-1, then it might just be more like using Black Market on each Cursed card in your hand but faster and cheaper.
The effect is interesting, and would make decks that use Cursed cards already stronger and perhaps even inspire some people to have specialized Cursed decks, but why did you give it Nature keyword? Or even Mage for that matter? That changes the effect in practice of both the Mage-summoning cards, Nature-summoning, and makes some Nature decks stronger (when they're already one of the strongest deck types) as well as making it easier to splash Nature in every other deck type.
To put it another way, the ideas of "a card that exploits your own Cursed cards to even more effect" and "a new uncommon Mage" and "an extremely cheap gems-cost Nature card" each individually make a card that could be worth adding, but they would all need to be balanced differently, and together they're stronger than the sum of their parts...
...particularly for that Ice Queen deck of yours Coolis which already has a very high winrate. ;} This basically adds the power of wrecking your opponent's hand for free to your favorite deck, and you'd only need to draw this two or three times to leave your opponent paralyzed with Ancient Castle and Ice Queens, the latter of which are usually useless to them and always give bonuses to you. =} A completely broken combination, in other words.
Maybe we could add something like this if there were also a bunch of different ways to deal with Cursed cards without playing them, as well as more practical strategies in general for handling the top 4-5 highest winrate deck kinds, but that's certainly not the current state of the game.