At the beginning of your upkeep, choose target opponent. Until end of turn, that player can't cast spells, you may look at the top card of their library any time, you may play the top card of their library, and you may spend mana as though it were mana of any color to cast spells this way.

Casualty 2 (As you cast this spell, you may sacrifice a creature with power 2 or greater. When you do, copy this spell.)

Each opponent exiles the top card of their library. You may cast spells from among those cards this turn. If you cast a spell this way, pay life equal to that spell's mana value rather than pay its mana cost.

Xantcha, Sleeper Agent enters the battlefield under the control of an opponent of your choice.

Xantcha attacks each combat if able and can't attack its owner or planeswalkers its owner controls.

: Xantcha's controller loses 2 life and you draw a card. Any player may activate this ability.

Flying

Whenever Xantid Swarm attacks, defending player can't cast spells this turn.

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)

, : Put a petrification counter on target creature. It gains defender and becomes a colorless artifact in addition to its other types. Its activated abilities can't be activated. (A creature with defender can't attack.)

Hexproof (This creature can't be the target of spells or abilities your opponents control.)

: Until end of turn, Xathrid Slyblade loses hexproof and gains first strike and deathtouch. (It deals combat damage before creatures without first strike. Any amount of damage it deals to a creature is enough to destroy it.)

Indestructible

As long as your devotion to red and green is less than seven, Xenagos isn't a creature.

At the beginning of combat on your turn, another target creature you control gains haste and gets +X/+X until end of turn, where X is that creature's power.

: Until your next upkeep, target noncreature artifact becomes an artifact creature with power and toughness each equal to its mana value.

Xenosquirrels enters the battlefield with two +1/+1 counters on it.

After you roll a die, you may remove a +1/+1 counter from Xenosquirrels. If you do, increase or decrease the result by 1.

Horsemanship (This creature can't be blocked except by creatures with horsemanship.)

Sacrifice Xiahou Dun, the One-Eyed: Return target black card from your graveyard to your hand. Activate only during your turn, before attackers are declared.

Flying, haste

Whenever Xira, the Golden Sting attacks, put an egg counter on another target creature without an egg counter on it. When that creature dies, if it has an egg counter on it, draw a card and create a 1/1 black Insect creature token with flying.

If you would create one or more Treasure tokens, instead create those tokens plus an additional Treasure token.

Flying

Whenever an opponent draws a card except the first one they draw in each of their draw steps, create a 1/1 green Snake creature token.

Whenever Xyris, the Writhing Storm deals combat damage to a player, you and that player each draw that many cards.