@Luxuria Unus  
coughs. I blame druids’ endless bullshit for that.

@Chaoslux  
Psst, nudge nudge. You’re thinking of Research Project.

@Whatsapokemon  
Yeah, Brann/Coldlight are wild only, but back in those days, mages didn’t have biology project (2 mana spell, Both players draw 2), primordial glyphs to discover more projects, shimmering tempests to get more glyphs, and elemental spellstones to get more glyphs and more projects. :D
 
This is obviously a farfetched scenario, but most likely one of the best class to pull off mill these days.

@Chaoslux
 
Hm, I didn’t think about enabling a mill deck. That could be an interesting application if you could give your opponents a bunch of high-cost cards. Coldlight got hall-of-famed though didn’t it? There’s not quite as many options available to do mill as there used to be.

@End Credicts  
Ysera is an really easy pick there. It doesnt have taunt, costs 9 mana so you cant even hero power on the turn you play her, much less do anything that you intended to do. Not enough damage to actually pressure you compared to LK, and you potentially cant play them for another turn or two. Since Ysera also puts cards in your hand, they will perpetually mill cards if they play her.
 
You just have to figure out how to fatigue them before you get overwhelmed :P

@Whatsapokemon  
That would make it overpowered I think and a no brainer that EVERYONE would play that card, even if there is no combos to counter. Destroying your entire opponent’s hand sounds broken and unfun on so many levels.
 
I really like the design of this card because its not just blatantly overpowered for the sake of it, also fits Rarity’s generous theme very well. Giving value to your opponent is a high cost, so you want it to be worth it.
 
On its own, it would burn one card. Sometimes one card is enough (Kingsbane, Shudderwock, Guldan, Frost Lich Jaina, …), but since it costs 7 mana, that means you can play Coldlight Oracle right after to make them draw two cards. Now you’re burning three. If you’re a Druid, you can decide to use Naturalize instead, making them burn five cards. Mages have similar options through Biology Project (and the various ways mages have to discount spells to fit more of them in as needed).
 
Burning three cards sounds like a great deal and very powerful, but at the same time, the cost is an equally powerful deal. If you burn low-value cards, then you only made them get closer to their combos AND you’ve given them more cards to play against you.
 
In other words, great design, very thematic. Would definitely play it in my mill decks, but this card will never see competitive play. (For those unfamiliar, this isnt a bad thing. Lots of great cards dont see competitive play, because fair and balanced isn’t good enough.)

>Plays Rarity  
>Discovers a Lich King, Yesera and King Crush  
>Thank you very much Rarity

Previous cards that have said “fill your hand with ___” haven’t replaced cards in the hand. With that in mind, I don’t think a card like this would be an effective combo breaker because it’d just cause your enemy to burn 1 card on their next draw since their hand would be full.
 
Did you mean to write “Discover a minion and replace your opponent’s hand with copies of that minion”?