Saskia the Unyielding

Vigilance, haste
As Saskia the Unyielding enters, choose a player.
Whenever a creature you control deals combat damage to a player, it deals that much damage to the chosen player.

Crux of Fate

Choose one —
• Destroy all Dragon creatures.
• Destroy all non-Dragon creatures.

Karrthus, Tyrant of Jund

Flying, haste
When Karrthus, Tyrant of Jund enters, gain control of all Dragons, then untap all Dragons.
Other Dragon creatures you control have haste.

Containment Priest

Flash
If a nontoken creature would enter and it wasn't cast, exile it instead.

Magus of the Moon

Rashida Scalebane

{T}: Destroy target attacking or blocking Dragon. It can't be regenerated. You gain life equal to its power.

Riders of Gavony

Vigilance
As Riders of Gavony enters, choose a creature type.
Human creatures you control have protection from creatures of the chosen type.

Hivis of the Scale

You may choose not to untap Hivis of the Scale during your untap step.
{T}: Gain control of target Dragon for as long as you control Hivis and Hivis remains tapped.

Whiptongue Hydra

Reach
When Whiptongue Hydra enters, destroy all creatures with flying. Put a +1/+1 counter on Whiptongue Hydra for each creature destroyed this way.

Lapse of Certainty

Counter target spell. If that spell is countered this way, put it on top of its owner's library instead of into that player's graveyard.

Natural Balance

Each player who controls six or more lands chooses five lands they control and sacrifices the rest. Each player who controls four or fewer lands may search their library for up to X basic land cards and put them onto the battlefield, where X is five minus the number of lands they control. Then each player who searched their library this way shuffles.

An-Zerrin Ruins

As An-Zerrin Ruins enters, choose a creature type.
Creatures of the chosen type don't untap during their controllers' untap steps.

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.

Chaosphere

Creatures with flying can block only creatures with flying.
Creatures without flying have reach. (They can block creatures with flying.)

Magus of the Balance

{4}{W}, {T}, Sacrifice Magus of the Balance: Each player chooses a number of lands they control equal to the number of lands controlled by the player who controls the fewest, then sacrifices the rest. Players discard cards and sacrifice creatures the same way.

Sandwurm Convergence

Creatures with flying can't attack you or planeswalkers you control.
At the beginning of your end step, create a 5/5 green Wurm creature token.

Crackdown

Nonwhite creatures with power 3 or greater don't untap during their controllers' untap steps.

Katabatic Winds

Phasing (This phases in or out before you untap during each of your untap steps. While it's phased out, it's treated as though it doesn't exist.)
Creatures with flying can't attack or block, and their activated abilities with {T} in their costs can't be activated.