You may have Altered Ego enter the battlefield as a copy of any creature on the battlefield, except it enters with X additional +1/+1 counters on it.
0 /
0
{X}{G}
Animist's Awakening
Sorcery
Reveal the top X cards of your library. Put all land cards from among them onto the battlefield tapped and the rest on the bottom of your library in a random order.
Spell mastery -- If there are two or more instant and/or sorcery cards in your graveyard, untap those lands.
{2}{G}
Beast Within
Instant
Destroy target permanent. Its controller creates a 3/3 green Beast creature token.
{X}{U}{U}{U}
Blue Sun's Zenith
Instant
Target player draws X cards. Shuffle Blue Sun's Zenith into its owner's library.
{2}{G}
Cultivate
Sorcery
Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.
{X}{U}{U}
Curse of the Swine
Sorcery
Exile X target creatures. For each creature exiled this way, its controller creates a 2/2 green Boar creature token.
{2}
Doubling Cube
Artifact
{3}, {T}: Double the amount of each type of unspent mana you have.
{X}{U}{U}
Finale of Revelation
Sorcery
Draw X cards. If X is 10 or more, instead shuffle your graveyard into your library, draw X cards, untap up to five lands, and you have no maximum hand size for the rest of the game.
Exile Finale of Revelation.
{X}{X}{G}
Gelatinous Genesis
Sorcery
Create X X/X green Ooze creature tokens.
{X}{G}{G}
Genesis Hydra
Creature - Plant Hydra
When you cast this spell, reveal the top X cards of your library. You may put a nonland permanent card with mana value X or less from among them onto the battlefield. Then shuffle the rest into your library.
Genesis Hydra enters the battlefield with X +1/+1 counters on it.
0 /
0
{G}{U}
Growth Spiral
Instant
Draw a card. You may put a land card from your hand onto the battlefield.
{X}{G}
Hungering Hydra
Creature - Hydra
Hungering Hydra enters the battlefield with X +1/+1 counters on it.
Hungering Hydra can't be blocked by more than one creature.
Whenever Hungering Hydra is dealt damage, put that many +1/+1 counters on it. (It must survive the damage to get the counters.)
0 /
0
{4}{G}{G}
Hydra Broodmaster
Creature - Hydra
{X}{X}{G}: Monstrosity X. (If this creature isn't monstrous, put X +1/+1 counters on it and it becomes monstrous.)
When Hydra Broodmaster becomes monstrous, create X X/X green Hydra creature tokens.
7 /
7
{X}{G}{U}
Hydroid Krasis
Creature - Jellyfish Hydra Beast
When you cast this spell, you gain half X life and draw half X cards. Round down each time.
Flying, trample
Hydroid Krasis enters the battlefield with X +1/+1 counters on it.
0 /
0
{2}{G}
Kodama's Reach
Sorcery - Arcane
Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.
{X}{G}{G}{G}
Lifeblood Hydra
Creature - Hydra
Trample
Lifeblood Hydra enters the battlefield with X +1/+1 counters on it.
When Lifeblood Hydra dies, you gain life and draw cards equal to its power.
0 /
0
{4}{G}{G}
Mana Reflection
Enchantment
If you tap a permanent for mana, it produces twice as much of that mana instead.
{X}{X}{U}{U}{U}{U}
Mass Manipulation
Sorcery
Gain control of X target creatures and/or planeswalkers.
{X}{G}
Mistcutter Hydra
Creature - Hydra
This spell can't be countered.
Haste, protection from blue
Mistcutter Hydra enters the battlefield with X +1/+1 counters on it.
0 /
0
{4}{G}{G}{G}
Nyxbloom Ancient
Enchantment Creature - Elemental
Trample
If you tap a permanent for mana, it produces three times as much of that mana instead.
5 /
5
{G}{G}{U}{U}
Plasm Capture
Instant
Counter target spell. At the beginning of your next precombat main phase, add X mana in any combination of colors, where X is that spell's mana value.
{X}{U}{U}
Pull from Tomorrow
Instant
Draw X cards, then discard a card.
{3}{G}{G}
Seedborn Muse
Creature - Spirit
Untap all permanents you control during each other player's untap step.
2 /
4
{X}{G}{G}
Steelbane Hydra
Creature - Turtle Hydra
Steelbane Hydra enters the battlefield with X +1/+1 counters on it.
{2}{G}, Remove a +1/+1 counter from Steelbane Hydra: Destroy target artifact or enchantment.
0 /
0
{X}{2}{U}
Stroke of Genius
Instant
Target player draws X cards.
{2}{G}
Unbound Flourishing
Enchantment
Whenever you cast a permanent spell with a mana cost that contains {X}, double the value of X.
Whenever you cast an instant or sorcery spell or activate an ability, if that spell's mana cost or that ability's activation cost contains {X}, copy that spell or ability. You may choose new targets for the copy.
{X}{G}{G}
Voracious Hydra
Creature - Hydra
Trample
Voracious Hydra enters the battlefield with X +1/+1 counters on it.
When Voracious Hydra enters the battlefield, choose one --
• Double the number of +1/+1 counters on Voracious Hydra.
• Voracious Hydra fights target creature you don't control.
0 /
1
{X}{X}
Walking Ballista
Artifact Creature - Construct
Walking Ballista enters the battlefield with X +1/+1 counters on it.
{4}: Put a +1/+1 counter on Walking Ballista.
Remove a +1/+1 counter from Walking Ballista: It deals 1 damage to any target.
0 /
0
{3}{G}
Wilderness Reclamation
Enchantment
At the beginning of your end step, untap all lands you control.
{5}{G}{G}
Zendikar Resurgent
Enchantment
Whenever you tap a land for mana, add one mana of any type that land produced. (The types of mana are white, blue, black, red, green, and colorless.)
Whenever you cast a creature spell, draw a card.
{3}{G}{U}
Kruphix, God of Horizons
Legendary Enchantment Creature - God
Indestructible
As long as your devotion to green and blue is less than seven, Kruphix isn't a creature.
You have no maximum hand size.
If you would lose unspent mana, that mana becomes colorless instead.