Meltdown

Destroy each artifact with mana value X or less.

Thriving Skyclaw

Flying
When Thriving Skyclaw enters the battlefield, you get {E}{E}{E} (three energy counters).
Whenever Thriving Skyclaw attacks, you may pay {E}{E}{E}. If you do, put a +1/+1 counter on it.

Dreamdrinker Vampire

Lifelink
{1}{B}: Adapt 1. (If this creature has no +1/+1 counters on it, put a +1/+1 counter on it.)
Whenever one or more +1/+1 counters are put on Dreamdrinker Vampire, it gains menace until end of turn.

Infernal Captor

Exploit (When this creature enters the battlefield, you may sacrifice a creature.)
When Infernal Captor exploits a creature, gain control of target artifact or creature until end of turn. Untap that permanent. It gains haste until end of turn.

Accursed Marauder

When Accursed Marauder enters the battlefield, each player sacrifices a nontoken creature.

Mindless Conscription

When Mindless Conscription enters the battlefield and whenever you draw your third card each turn, amass Zombies 3. (Put three +1/+1 counters on an Army you control. It's also a Zombie. If you don't control an Army, create a 0/0 black Zombie Army creature token first.)

Breathe Your Last

Destroy target creature or planeswalker. You gain 1 life for each of its colors.

Fervent Charge

Whenever a creature you control attacks, it gets +2/+2 until end of turn.

Scurrilous Sentry

Menace
Whenever Scurrilous Sentry enters the battlefield or attacks, it connives. (Draw a card, then discard a card. If you discarded a nonland card, put a +1/+1 counter on this creature.)

Victimize

Choose two target creature cards in your graveyard. Sacrifice a creature. If you do, return the chosen cards to the battlefield tapped.

Galvanic Discharge

Choose target creature or planeswalker. You get {E}{E}{E} (three energy counters), then you may pay any amount of {E}. Galvanic Discharge deals that much damage to that permanent.

Buried Alive

Search your library for up to three creature cards, put them into your graveyard, then shuffle.

Glimpse the Impossible

Exile the top three cards of your library. You may play those cards this turn. At the beginning of the next end step, if any of those cards remain exiled, put them into your graveyard, then create a 0/1 colorless Eldrazi Spawn creature token for each card put into your graveyard this way. Those tokens have "Sacrifice this creature: Add {C}."

Siege Smash

Split second (As long as this spell is on the stack, players can't cast spells or activate abilities that aren't mana abilities.)
Choose one —
• Destroy target artifact.
• Target creature gets +3/+2 and gains trample until end of turn.

Vampire Spawn

When Vampire Spawn enters the battlefield, each opponent loses 2 life and you gain 2 life.

Electrozoa

Flash
Flying
When Electrozoa enters the battlefield, you get {E}{E} (two energy counters).
At the beginning of your precombat main phase, tap Electrozoa unless you pay {E}.

Voidpouncer

Devoid (This card has no color.)
Kicker {2}{C} (You may pay an additional {2}{C} as you cast this spell.)
If Voidpouncer was kicked, it enters the battlefield with two +1/+1 counters and a trample counter on it and with haste.

Red Dragon

Flying
Fire Breath — When Red Dragon enters the battlefield, it deals 4 damage to each opponent.

Thundering Rebuke

Thundering Rebuke deals 4 damage to target creature or planeswalker.

Teeterpeak Ambusher

{2}{R}: Teeterpeak Ambusher gets +2/+0 until end of turn.

Baleful Beholder

When Baleful Beholder enters the battlefield, choose one —
• Antimagic Cone — Each opponent sacrifices an enchantment.
• Fear Ray — Creatures you control gain menace until end of turn. (A creature with menace can't be blocked except by two or more creatures.)

Black Dragon

Flying
Acid Breath — When Black Dragon enters the battlefield, target creature an opponent controls gets -3/-3 until end of turn.

Wither and Bloom

Target creature gets -3/-3 until end of turn.
{1}{B}, Exile Wither and Bloom from your graveyard: Put a +1/+1 counter on target creature you control. Activate only as a sorcery.

Atraxa, Praetors' Voice

Flying, vigilance, deathtouch, lifelink
At the beginning of your end step, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Fanged Flames

Devoid (This card has no color.)
Fanged Flames deals 4 damage to target creature or planeswalker. If that creature or planeswalker would die this turn, exile it instead.

Ardent Elementalist

When Ardent Elementalist enters the battlefield, return target instant or sorcery card from your graveyard to your hand.

Axgard Cavalry

{T}: Target creature gains haste until end of turn.

Fetid Gargantua

{2}{B}: Adapt 2. (If this creature has no +1/+1 counters on it, put two +1/+1 counters on it.)
Whenever one or more +1/+1 counters are put on Fetid Gargantua, you may draw two cards. If you do, you lose 2 life.

Powerbalance

Whenever an opponent casts a spell, you may reveal the top card of your library. If you do, you may cast that card without paying its mana cost if the two spells have the same mana value.