Boreas Charger

Flying
When Boreas Charger leaves the battlefield, choose an opponent who controls more lands than you. Search your library for a number of Plains cards equal to the difference, reveal those cards, put one of them onto the battlefield tapped and the rest into your hand, then shuffle.

Plains

Pegasus Stampede

Buyback—Sacrifice a land. (You may sacrifice a land in addition to any other costs as you cast this spell. If you do, put this card into your hand as it resolves.)
Create a 1/1 white Pegasus creature token with flying.

Gift of Estates

If an opponent controls more lands than you, search your library for up to three Plains cards, reveal them, put them into your hand, then shuffle.

Serra Angel

Flying
Vigilance (Attacking doesn't cause this creature to tap.)

Boros Garrison

Boros Garrison enters tapped.
When Boros Garrison enters, return a land you control to its owner's hand.
{T}: Add {R}{W}.

Land's Edge

Discard a card: If the discarded card was a land card, Land's Edge deals 2 damage to target player or planeswalker. Any player may activate this ability.

Spirit Link

Enchant creature (Target a creature as you cast this. This card enters attached to that creature.)
Whenever enchanted creature deals damage, you gain that much life.

Mountain

White Knight

First strike (This creature deals combat damage before creatures without first strike.)
Protection from black (This creature can't be blocked, targeted, dealt damage, or enchanted by anything black.)

Mother of Runes

{T}: Target creature you control gains protection from the color of your choice until end of turn.

Pacifism

Enchant creature
Enchanted creature can't attack or block.

Scroll Rack

{1}, {T}: Exile any number of cards from your hand face down. Put that many cards from the top of your library into your hand. Then look at the exiled cards and put them on top of your library in any order.

Land Tax

At the beginning of your upkeep, if an opponent controls more lands than you, you may search your library for up to three basic land cards, reveal them, put them into your hand, then shuffle.