Eiganjo Exemplar

Whenever a Samurai or Warrior you control attacks alone, it gets +1/+1 until end of turn.

Alpine Meadow

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

Sunblade Samurai

Vigilance (Attacking doesn't cause this creature to tap.)
Channel — {2}, Discard Sunblade Samurai: Search your library for a basic Plains card, reveal it, put it into your hand, then shuffle. You gain 2 life.

Snow-Covered Mountain

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Imperial Subduer

Whenever a Samurai or Warrior you control attacks alone, tap target creature you don't control.

Gods Willing

Target creature you control gains protection from the color of your choice until end of turn. (It can't be blocked, targeted, dealt damage, enchanted, or equipped by anything of that color.)
Scry 1.

Ancestral Katana

Whenever a Samurai or Warrior you control attacks alone, you may pay {1}. When you do, attach Ancestral Katana to it.
Equipped creature gets +2/+1.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Skred

Skred deals damage to target creature equal to the number of snow permanents you control.

Peerless Samurai

Menace (This creature can't be blocked except by two or more creatures.)
Whenever a Samurai or Warrior you control attacks alone, the next spell you cast this turn costs {1} less to cast.

Snow-Covered Plains

Prismatic Strands

Prevent all damage that sources of the color of your choice would deal this turn.
Flashback—Tap an untapped white creature you control. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Goblin Champion

Haste
Exalted (Whenever a creature you control attacks alone, that creature gets +1/+1 until end of turn.)

Akki Ronin

Whenever a Samurai or Warrior you control attacks alone, you may discard a card. If you do, draw a card.