Put three -1/-1 counters on target attacking or blocking creature.

When this Rift enters or is traversed, if you have less life than an opponent, you gain 3 life. If you control fewer creatures than an opponent, create two tapped 1/1 colorless Reflection creature tokens. If you have fewer cards in hand than an opponent, draw a card.
Traverse 3

When Courtless Spiritcaller enters, create a 1/1 white Spirit creature token with flying.
{4}{W}, Sacrifice Courtless Spiritcaller: Create two 1/1 white Spirit creature tokens with flying.

Put target artifact or enchantment on the bottom of its owner's library.

Whenever another creature dies, if that creature had the greatest power or was tied for the greatest power, you gain 2 life and draw a card.

Until end of turn, each creature you control can't be blocked by more than one creature.
Maneuver

As an additional cost to cast this spell, sacrifice an artifact or creature, or pay 3 life.
Destroy target creature or planeswalker.

Whenever a Subroutine you control runs, exile the top card of your library face-down.
{R}, Discard your hand, Sacrifice this enchantment: Put all cards exiled with this enchantment into your hand.

When Crippling Hallucinations enters, investigate twice.
Whenever you sacrifice a Clue, you may tap target creature.

Exile target creature with flying.

As Crownguard Ban enters, choose a card name.
Spells with the chosen name can't be cast.
{3}, Exile a card from your hand with the chosen name: Draw a card. Any player may activate this ability.

When Crownguard Instructor enters, put a vigilance counter on target creature you control.

Target creature you control deals damage equal to its toughness to another target creature.

As an additional cost to cast this spell, exile a card from your graveyard.
Search your library for a card with the same mana value as the exiled card, reveal it, put it into your hand, then shuffle. You lose 2 life.

Crystal Cuirass enters with two +1/+1 counters on it.
Whenever Crystal Cuirass becomes attached to a creature, move all counters from Crystal Cuirass onto that creature.
Whenever Crystal Cuirass becomes unattached from equipped creature, if that creature had counters on it, put those counters on Crystal Cuirass.
Equip {3}

Vigilance, trample
When Crystal Lion enters, crystallize.

Flash
Haste
When Cuernas, Victor of the Ring enters, it and other legendary creatures you control gain trample and indestructible until end of turn.

Master of Monument to the Thirty
{30}: Curator of Myth deals 30 damage to any target.

Experience
Curious Cubs has first strike as long as its attacking.
When Curious Cubs has three or more +1/+1 counters on it, remove them all and transform it.

Counter target spell with mana value 3 or less.

Destroy target attacking or blocking creature with power 3 or less. Scry 1.

Level up {1}{G}
[level 1-2] Whenever you cast a creature spell with power 3 or greater, draw a card.
[level 3+] Whenever you cast a creature spell with power 3 or greater, copy it.

Vigilance
As Cybres-Clan Arbiter enters, look at an opponent's hand, then choose a noncreature card name.
Spells with the chosen name cost {2} more to cast.

Whenever another Centaur you control enters, put a +1/+1 counter on Cybres-Clan Squire.