Burnout

Counter target instant spell if it's blue.
Draw a card at the beginning of the next turn's upkeep.

Guttural Response

Artifact Blast

Green Slime

Flash
When Green Slime enters the battlefield, counter target activated or triggered ability from an artifact or enchantment source. If a permanent's ability is countered this way, destroy that permanent.
Foretell {G} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)

Celestial Dawn

Lands you control are Plains.
Nonland permanents you control are white. The same is true for spells you control and nonland cards you own that aren't on the battlefield.
You may spend white mana as though it were mana of any color. You may spend other mana only as though it were colorless mana.

Grindstone

{3}, {T}: Target player mills two cards. If two cards that share a color were milled this way, repeat this process.

Tibalt's Trickery

Counter target spell. Choose 1, 2, or 3 at random. Its controller mills that many cards, then exiles cards from the top of their library until they exile a nonland card with a different name than that spell. They may cast that card without paying its mana cost. Then they put the exiled cards on the bottom of their library in a random order.

Planar Chaos

At the beginning of your upkeep, flip a coin. If you lose the flip, sacrifice Planar Chaos.
Whenever a player casts a spell, that player flips a coin. If they lose the flip, counter that spell.

Chancellor of the Annex

You may reveal this card from your opening hand. If you do, when each opponent casts their first spell of the game, counter that spell unless that player pays {1}.
Flying
Whenever an opponent casts a spell, counter it unless that player pays {1}.

Rith, the Awakener

Flying
Whenever Rith, the Awakener deals combat damage to a player, you may pay {2}{G}. If you do, choose a color, then create a 1/1 green Saproling creature token for each permanent of that color.

Bind

Counter target activated ability. (Mana abilities can't be targeted.)
Draw a card.

Painter's Servant

As Painter's Servant enters the battlefield, choose a color.
All cards that aren't on the battlefield, spells, and permanents are the chosen color in addition to their other colors.

Order of the Sacred Torch

{T}, Pay 1 life: Counter target black spell.

Rebuff the Wicked

Counter target spell that targets a permanent you control.

Mages' Contest

You and target spell's controller bid life. You start the bidding with a bid of 1. In turn order, each player may top the high bid. The bidding ends if the high bid stands. The high bidder loses life equal to the high bid. If you win the bidding, counter that spell.