Transcend Nature4UUU
Sorcery (M)
Exile all cards from your graveyard. Put your all cards from library into your graveyard, then shuffle all cards exiled by ~ into your library.
Mangrove Colony1G
Creature - Plant (R)
Creature - Plant
~ enters the battlefield with a +1/+1 counter on it.
At the end of each turn, you may pay 1G. If you do, double the number of +1/+1 counters on ~.
Marsh Parasite1B
Creature - Plant Zombie (U)
~ can't be blocked.
Whenever ~ attacks, another target creature you control gains deathtouch until end of turn.
1/1
I know it's ironic for me to say this given your username, but I've always thought that what you called illuminate should be flashback on permanents, not unearth. I like the card as is, but I would have probably liked it even more if it were sacrifice instead of exile but with a higher illuminate cost and some kind of exile clause included in the keyword. But I get that you probably went with the shortest text for elegance, and I honestly can't blame you. Also, rarity is missing, but I like the idea so much that I'm voting for it anyway.
Thanks for the kind words, and for the feedback.
This is basically a product of me running out of ideas and digging up half-baked set mechanic ideas I had from a while ago. This particular one was supposed to have a bunch of artifacts and enchantments with this ability, and some could exile themselves whereas some have static effects. I was going to put a ton of looter-ish effects in to support it, and also some exile matters mechanic too. I thought it was interesting to have a flashback-like effect that explicitly didn't allow you to use it for a double effect.
The way to do it is either to "Illuminate" it with a counter on it, and if it would die with a counter on it, exile it instead, or alternately to just use Embalm. Unearth is a mechanic I like a lot (obviously) but I do agree with you that it would be better to do an effect like Embalm while trying to minimize tracking problems.
The rarity on this one is difficult, in a full set where this would be relevant, it would probably NEED to be rare, but if it were part of a precon, or modern horizon auxiliary set, maybe uncommon though maybe 1 more? Ugh.
Mercurial SliverUU
Creature - Sliver Shapeshifter (R)
You may have ~ enter the battlefield as a copy of any sliver on the battlefield. When the hive happens upon a particularly useful mutation it can often draw the ire of other mortal races, so the local queen sets about replicating the success before the original is killed.
2/2
I think you can make the case for this as uncommon in some sets. I think if you have uncommons such as Might Sliver, things could get out of hand in limited. Also you'd have to watch for convoluted effects (can't think of an existing sliver like this, but if you did something that created a loop effect or some kind of non-intuitive interaction, you'd probably want to put this at rare. If you avoid those pitfalls, I think this is much less problematic uncommon than most clones would be. You can make sure you don't get a really powerful effect too often, and it should hopefully be easier to track when you're almost never copying an opponent's creature.
Also one thing to watch for would be if you have a high volume of non-stackable sliver abilities and/or non-battlefield sliver abilities. I'd suspect that most sliver abilities aren't stackable, which would reduce the appeal of this card - there is still some value in redundancy, but I think it probably undercuts the excitement of this card - you might as well make a dive down for slivers at that point.
Automimic2U
Creature - Shapeshifter (R)
You may have Automimic enter the battlefield as a copy of any creature on the battlefield with converted mana cost 3 or less.
Telescopic PrismX1
Artifact (U)
~ enters the battlefield, put X charge couners on ~. 1, T: Add X mana of any one color to your mana pool for each charge counter on ~.
Goblin Delegation 2R
Instant (C)
Create two 1/1 red Goblin tokens.
Addendum - if it's your main phase, those creatures gain haste until end of turn.
Transcend Nature 4UUU
Sorcery (M)
Exile all cards from your graveyard. Put your all cards from library into your graveyard, then shuffle all cards exiled by ~ into your library.
Mangrove Colony 1G
Creature - Plant (R)
Creature - Plant
~ enters the battlefield with a +1/+1 counter on it.
At the end of each turn, you may pay 1G. If you do, double the number of +1/+1 counters on ~.
Remnant of Paradise 3G
Artifact (U)
T: Add 2 mana of any one color to your mana pool.
Temporal Replicator 4
Artifact (U)
2, T: Copy target instant or sorcery spell that costs 3 or less.
Marsh Parasite 1B
Creature - Plant Zombie (U)
~ can't be blocked.
Whenever ~ attacks, another target creature you control gains deathtouch until end of turn.
1/1
False Target B
Instant (C)
As an additional cost to cast ~, sacrifice a creature.
Target creature is indestructible this turn.
Thanks for the kind words, and for the feedback.
This is basically a product of me running out of ideas and digging up half-baked set mechanic ideas I had from a while ago. This particular one was supposed to have a bunch of artifacts and enchantments with this ability, and some could exile themselves whereas some have static effects. I was going to put a ton of looter-ish effects in to support it, and also some exile matters mechanic too. I thought it was interesting to have a flashback-like effect that explicitly didn't allow you to use it for a double effect.
The way to do it is either to "Illuminate" it with a counter on it, and if it would die with a counter on it, exile it instead, or alternately to just use Embalm. Unearth is a mechanic I like a lot (obviously) but I do agree with you that it would be better to do an effect like Embalm while trying to minimize tracking problems.
Near Miss 1U
Instant (C)
Target creature gets +0/+3 until end of turn.
Draw a card.
Prophecy of Fire 2R
Enchantment
Exile ~: ~ deals 3 damage to any target.
Illuminate 2R (You may cast this card from your graveyard for 2R.)
I think you can make the case for this as uncommon in some sets. I think if you have uncommons such as Might Sliver, things could get out of hand in limited. Also you'd have to watch for convoluted effects (can't think of an existing sliver like this, but if you did something that created a loop effect or some kind of non-intuitive interaction, you'd probably want to put this at rare. If you avoid those pitfalls, I think this is much less problematic uncommon than most clones would be. You can make sure you don't get a really powerful effect too often, and it should hopefully be easier to track when you're almost never copying an opponent's creature.
Also one thing to watch for would be if you have a high volume of non-stackable sliver abilities and/or non-battlefield sliver abilities. I'd suspect that most sliver abilities aren't stackable, which would reduce the appeal of this card - there is still some value in redundancy, but I think it probably undercuts the excitement of this card - you might as well make a dive down for slivers at that point.
Automimic 2U
Creature - Shapeshifter (R)
You may have Automimic enter the battlefield as a copy of any creature on the battlefield with converted mana cost 3 or less.
Telescopic Prism X1
Artifact (U)
~ enters the battlefield, put X charge couners on ~.
1, T: Add X mana of any one color to your mana pool for each charge counter on ~.
Arcane Tutor 1WU
Sorcery (R)
Search your library for an artifact or enchantment card, reveal it, and put it into your hand. Then shuffle your library.
Diabolic Seal 2B
Enchantment
Sacrifice ~: Target player sacrifices a tapped creature.