Counter target spell, activated ability, or triggered ability. (Mana abilities can't be targeted.)

Attacking Pests you control get +1/+0 and have menace.
Whenever a nontoken creature you control dies, create a 1/1 black and green Pest creature token with "When this token dies, you gain 1 life."

Exile target creature.

Improvise (Your artifacts can help cast this spell. Each artifact you tap after you're done activating mana abilities pays for .)
Draw X cards.

Whenever you cast an instant or sorcery spell, this creature deals 2 damage to each opponent.

Create two 1/1 colorless Sliver creature tokens.

Each player shuffles their hand and graveyard into their library, then draws seven cards. (Then put Timetwister into its owner's graveyard.)

Flash
Reach
When this creature enters, up to one target player puts all the cards from their graveyard on the bottom of their library in a random order.
Evoke—Exile a green card from your hand.

Vigilance

If a red or artifact source you control would deal damage to an opponent or a permanent an opponent controls, it deals that much damage plus 1 instead.

Equipped creature gets +2/+0 and has trample.
Whenever equipped creature deals combat damage to a player, create that many 1/1 green and white Citizen creature tokens.
Equip

Counter target spell. If that spell is countered this way, put that card on your choice of the top or bottom of its owner's library instead of into that player's graveyard.

When this creature enters, you may search your library for a creature card with mana value 1 or less, reveal it, put it into your hand, then shuffle.
Sacrifice this creature: Your opponents can't cast noncreature spells this turn.

First strike, deathtouch
Whenever a creature an opponent controls dies, you may return target artifact card from your graveyard to your hand.

At the beginning of each end step, put a +1/+1 counter on this creature for each creature that died this turn.

, , Discard a card: Destroy target blue permanent.
, , Discard a card: Jaya Ballard deals 3 damage to any target. A creature dealt damage this way can't be regenerated this turn.
, , Discard a card: Jaya Ballard deals 6 damage to each creature and each player.

+2: Each player draws a card.
−1: Target player draws a card.
−10: Target player mills twenty cards.

Devoid (This card has no color.)
All creatures get -2/-2 until end of turn. If a creature would die this turn, exile it instead.

Equipped creature gets +2/+2 and has protection from black and from red.
Whenever equipped creature deals combat damage to a player, destroy up to one target planeswalker and up to one target artifact.
Equip

Flash
Whenever you cast another spell that has flash, you draw a card and each opponent loses 1 life.

You may choose not to untap this creature during your untap step.
: Gain control of target creature with power less than or equal to this creature's power for as long as this creature remains tapped and that creature's power remains less than or equal to this creature's power.

You have hexproof. (You can't be the target of spells or abilities your opponents control.)
−2: Create a 0/3 white Wall creature token with defender.

Flying
Each player can't cast more than one spell each turn.
Nonbasic lands your opponents control enter tapped.

Converge — Radiant Flames deals X damage to each creature, where X is the number of colors of mana spent to cast this spell.

: Add .

Ninjutsu (, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Whenever Nashi deals combat damage to a player, exile the top card of each player's library. Until end of turn, you may play one of those cards. If you cast a spell this way, pay life equal to its mana value rather than paying its mana cost.

Equipped creature gets +2/+2 and has protection from black and from green.
Whenever equipped creature deals combat damage to a player, that player discards a card and you untap all lands you control.
Equip

Flying
Whenever a player attacks one of your opponents, if that opponent has more life than another of your opponents, that attacking player draws a card and you put two +1/+1 counters on a creature you control.

Flash
Haste

Lifelink
At the beginning of each of your postcombat main phases, you may pay X life, where X is the number of opponents that were dealt combat damage this turn. If you do, draw X cards.
Partner (You can have two commanders if both have partner.)

Enchant creature
Enchanted creature gets +3/+1, has flying, and is a Demon in addition to its other types.
You may cast this card from your graveyard by paying 3 life and discarding a card in addition to paying its other costs.

Target opponent gains control of target creature. (If an attacking or blocking creature changes controllers, it's removed from combat.)

Sacrifice a creature. Rupture deals damage equal to that creature's power to each creature without flying and each player.

Whenever a creature you control becomes blocked, you may return it to its owner's hand.
Whenever one or more creatures you control deal combat damage to a player, draw a card.

+1: Whenever one or more creatures you control deal combat damage to a player this turn, draw a card, then discard a card.
−2: Create a 2/2 blue Illusion creature token with "When this token becomes the target of a spell, sacrifice it."
−5: Create two tokens that are copies of Jace, except they're not legendary.

Vigilance, menace, lifelink
Creature cards in graveyards can't enter the battlefield.
Players can't cast spells from graveyards.