Iceberg Cancrix

Whenever another snow permanent you control enters, you may have target player mill two cards.

Icehide Golem

({S} can be paid with one mana from a snow source.)

Snow-Covered Island

Rime Transfusion

Enchant creature
Enchanted creature gets +2/+1 and has "{S}: This creature can't be blocked this turn except by snow creatures." ({S} can be paid with one mana from a snow source.)

Chilling Shade

Flying
{S}: Chilling Shade gets +1/+1 until end of turn. ({S} can be paid with one mana from a snow source.)

Entering

Put a creature card from a graveyard onto the battlefield under your control. It gains haste until end of turn.
Fuse (You may cast one or both halves of this card from your hand.)

Breaking

Target player mills eight cards.
Fuse (You may cast one or both halves of this card from your hand.)

Breaking // Entering

Glimpse the Unthinkable

Negate

Winter's Rest

Enchant creature
When Winter's Rest enters, tap enchanted creature.
As long as you control another snow permanent, enchanted creature doesn't untap during its controller's untap step.

Frost Marsh

Frost Marsh enters tapped.
{T}: Add {U} or {B}.

Dead of Winter

All nonsnow creatures get -X/-X until end of turn, where X is the number of snow permanents you control.

Hedron Crab

Landfall — Whenever a land you control enters, target player mills three cards.

Snow-Covered Swamp

Marit Lage's Slumber

Whenever Marit Lage's Slumber or another snow permanent you control enters, scry 1.
At the beginning of your upkeep, if you control ten or more snow permanents, sacrifice Marit Lage's Slumber. If you do, create Marit Lage, a legendary 20/20 black Avatar creature token with flying and indestructible.

Choked Estuary

As Choked Estuary enters, you may reveal an Island or Swamp card from your hand. If you don't, Choked Estuary enters tapped.
{T}: Add {U} or {B}.