Whiteout

All creatures lose flying until end of turn.
Sacrifice a snow land: Return Whiteout from your graveyard to your hand.

Tireless Tribe

Discard a card: Tireless Tribe gets +0/+4 until end of turn.

Alpine Meadow

({T}: Add {R} or {W}.)
Alpine Meadow enters the battlefield tapped.

Snow-Covered Plains

Inside Out

Switch target creature's power and toughness until end of turn.
Draw a card.

Wild Mongrel

Discard a card: Wild Mongrel gets +1/+1 and becomes the color of your choice until end of turn.

Aurora Eidolon

{W}, Sacrifice Aurora Eidolon: Prevent the next 3 damage that would be dealt to any target this turn.
Whenever you cast a multicolored spell, you may return Aurora Eidolon from your graveyard to your hand.

Safewright Quest

Search your library for a Forest or Plains card, reveal it, put it into your hand, then shuffle.

Snow-Covered Forest

About Face

Switch target creature's power and toughness until end of turn.

Arctic Treeline

({T}: Add {G} or {W}.)
Arctic Treeline enters the battlefield tapped.

Double Cleave

Target creature gains double strike until end of turn. (It deals both first-strike and regular combat damage.)

Verdant Eidolon

{G}, Sacrifice Verdant Eidolon: Add three mana of any one color.
Whenever you cast a multicolored spell, you may return Verdant Eidolon from your graveyard to your hand.

Highland Forest

({T}: Add {R} or {G}.)
Highland Forest enters the battlefield tapped.

Shield of the Oversoul

Enchant creature
As long as enchanted creature is green, it gets +1/+1 and has indestructible. (Damage and effects that say "destroy" don't destroy it. If its toughness is 0 or less, it's still put into its owner's graveyard.)
As long as enchanted creature is white, it gets +1/+1 and has flying.