Round 2 option: Black/Food

Skewer B
Sorcery {U}
Destroy target creature. Its controller creates a Food token. (It's an artifact with "2, T, Sacrifice this artifact: You gain 3 life.")
"You didn't think I was going to hand your foe to you on a silver platter?"

Round 1 option: Adamant

Reflective Thoughts 2U
Sorcery {U}
Each player draws three cards.
Adamant - If at least three blue mana was spent to cast this spell, instead only you draw three cards.
Inside Vantress' mirrorhall, the thoughts of one are the thoughts of all.

R1: Non-black Blood R2: Non-red Stone + Non-green Flesh Mergo the Stonegrafter 2WW Legendary Creature - Kor Artificer {R} At the beginning of your upkeep, you may put a petrification counter on target non-artifact creature. Creatures with petrification counters on them are indestructible, can't atta...

Element: Blood (Non-Black)

Bloodshot Frenzy 1RR
Enchantment - Aura {U}
Enchant creature
When Bloodshot Frenzy enters the battlefield, draw a card.
Enchanted creature gets +X/-X and has trample, where X is its base toughness minus 1.
Enchanted creature gets +1/-1 for each +1/+1 counter on it.

September: Does "Pay X life" qualify?

Complaetion Engine 6
Artifact {R}
When Complaetion Engine enters the battlefield, you may pay X life. If you do, put X -1/-1 counters on each creature.
B, T, Pay X life: Put X -1/-1 counters on target creature.

barbecube: This is perfect for a Limited set with a high power level, such as any of the premium booster products like Modern Horizons. If there's a mono-white aggro deck out there, this will see play in it as it's extremely difficult for midrange decks to remove and can give the aggressive decks qu...

Eidren, Perfect of Lys Alana 2BG Legendary Creature - Elf Warrior {M} Reach, deathtouch As Eidren, Perfect of Lys Alana enters the battlefield, choose a creature type other than Elf. Eidren has protection from the chosen type. Whenever another creature of the chosen type dies, you may draw a card. ...

A top 3 only, D&D ran late so I'm short on time

1) barbecube
2) bravelion83
3) Cardz5000

Ocean Devourer 3UUU Creature - Leviathan {M} Trample Ocean Devourer's base power and toughness are each equal to the number of Islands on the battlefield. Ocean Devourer can't attack unless defending player controls at least three Islands. 1UU : Put a flood counter on target land. That land is an I...

Little short on time so top 3 only

1)Jimmy Groove
2)user_938036
3)Legend

netn10: Naxos, the Dealer - Reminds me a lot of Abyssal Persecutor. The modal drawback is intriguing. I think this could be a 7/6 even - similar cards such as Master of the Feast say this is slightly underpowered. I do like the way this works in multiplayer though. Gateways7: Enigma Swindler - I lik...

Interceptive Stance URW
Enchantment - Aura {R}
Flash
Enchant creature
Enchanted creature has indestructible.
When Interceptive Stance enters the battlefield, change a target of target spell or ability to enchanted creature.