Marioland
Although an interesting idea, there are a few very significant issues to address:
1: There's no timer between turns for you to actually choose a discovery effect, which makes the whole "discover between turns" thing impossible.
1b: Discovering things defaults to 3 options as well, so you don't need to specify that at all.
2: Kind ofa hask bimilackr ato 1b, but the wording is honestly clunky in general, which is probably the easiest to fix by replacing the text with "Discover a minion and turn into a copy of it for 2 turns".
2b: Once again, transforming back is also something that's assumed to restore the creature back to full health, and doesn't need to be specified. It's already intrinsic to transformation effects.
3: It's really, really swingy in a bad way, since it could become something like a turn 6 Deathwing at best or fall way under the bar when you pull a cluster of 1-5 mana minions or poorly statted high-effect based 6+ minions (e.g. Silver Vanguard in a deck with no 8 mana minions). At best it's ridiculously overpowered as you get a massive minion out 4 turns early, at worst it's so far under the power curve that it's not worthwhile and you spent 6 mana for a Knife Juggler or something.
All this being said, both in having a totally impossible effect, clunky wording that states intrinsic game information, and an insane amount of swinginess (about 70-80% underpowered, due to the high number of 1-5 mana minions and things like Silver Vanguard with powerful build-around effects and no stats and 20-30% overpowered when you get a turn 6 Lich King/Ysera/Deathwing or something), you might be able to salvage at least some part of the idea. Maybe make her like Taldaraam without the funky "no other 3 mana cards" triggerffect to become a 6/6 copy of a minion instead? Alternatively, discover a 6 mana minion instead so the pool is narrower and more fair for the cost?
1: There's no timer between turns for you to actually choose a discovery effect, which makes the whole "discover between turns" thing impossible.
1b: Discovering things defaults to 3 options as well, so you don't need to specify that at all.
2: Kind of
2b: Once again, transforming back is also something that's assumed to restore the creature back to full health, and doesn't need to be specified. It's already intrinsic to transformation effects.
3: It's really, really swingy
All this being said, both in having a totally impossible effect, clunky wording that states intrinsic game information, and an insane amount of swinginess