Astral Cornucopia enters the battlefield with X charge counters on it. {T}: Choose a color. Add one mana of that color for each charge counter on Astral Cornucopia.

Cryptic Trilobite enters the battlefield with X +1/+1 counters on it. Remove a +1/+1 counter from Cryptic Trilobite: Add {C}{C}. Spend this mana only to activate abilities. {1}, {T}: Put a +1/+1 counter on Cryptic Trilobite.

Endless One enters the battlefield with X +1/+1 counters on it.

Hangarback Walker enters the battlefield with X +1/+1 counters on it. When Hangarback Walker dies, create a 1/1 colorless Thopter artifact creature token with flying for each +1/+1 counter on Hangarback Walker. {1}, {T}: Put a +1/+1 counter on Hangarback Walker.

When Jadelight Spelunker enters the battlefield, it explores X times. (To have it explore, reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on that creature, then put the card back or put it into your graveyard.)

Trample, haste Lightning Serpent enters the battlefield with X +1/+0 counters on it. At the beginning of the end step, sacrifice Lightning Serpent.

Trample Ochre Jelly enters the battlefield with X +1/+1 counters on it. Split — When Ochre Jelly dies, if it had two or more +1/+1 counters on it, create a token that's a copy of it at the beginning of the next end step. The token enters the battlefield with half that many +1/+1 counters on it, rounded down.

Omarthis, Ghostfire Initiate enters the battlefield with X +1/+1 counters on it. Whenever you put one or more +1/+1 counters on another colorless creature, you may put a +1/+1 counter on Omarthis. When Omarthis dies, manifest a number of cards from the top of your library equal to the number of counters on it.

Defender (This creature can't attack.) Shifting Wall enters the battlefield with X +1/+1 counters on it.

Ravenous (This creature enters the battlefield with X +1/+1 counters on it. If X is 5 or more, draw a card when it enters.) Defender Spore Chimney — When Sporocyst enters the battlefield, search your library for up to X basic land cards, put them onto the battlefield tapped, then shuffle.

Ugin's Conjurant enters the battlefield with X +1/+1 counters on it. If damage would be dealt to Ugin's Conjurant while it has a +1/+1 counter on it, prevent that damage and remove that many +1/+1 counters from Ugin's Conjurant.

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.

Destroy target artifact. It can't be regenerated. Create X 1/1 green Saproling creature tokens, where X is that artifact's mana value.

Surge {X}{R} (You may cast this spell for its surge cost if you or a teammate has cast another spell this turn.) Fall of the Titans deals X damage to each of up to two targets.

As an additional cost to cast this spell, you may exile any number of red cards from your hand. This spell costs {2} less to cast for each card exiled this way. Exile the top X cards of your library. You may play up to two of those cards until the end of your next turn.

As an additional cost to cast this spell, you may exile any number of blue cards from your hand. This spell costs {2} less to cast for each card exiled this way. Up to X target creatures phase out. (While they're phased out, they're treated as though they don't exist. Each one phases in before its controller untaps during their next untap step.)

Destroy target artifact or enchantment with mana value X. It can't be regenerated. You gain X life.

Draw X cards, then discard X cards. Create a 1/1 white Spirit creature token with flying for each card type among cards discarded this way.

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.

Create X 1/1 green Forest Dryad land creature tokens. (They're affected by summoning sickness.)

Bonfire of the Damned deals X damage to target player or planeswalker and each creature that player or that planeswalker's controller controls. Miracle {X}{R} (You may cast this card for its miracle cost when you draw it if it's the first card you drew this turn.)

Search your library for a green creature card with mana value X or less, put it onto the battlefield, then shuffle. Shuffle Green Sun's Zenith into its owner's library.

Hell to Pay deals X damage to target creature. Create a number of tapped Treasure tokens equal to the amount of excess damage dealt to that creature this way.

Destroy up to X target artifacts and/or enchantments. Create twice X 1/1 black and green Pest creature tokens with "When this creature dies, you gain 1 life."