Shattered Angel

Flying
Whenever a land an opponent controls enters, you may gain 3 life.

Oreskos Explorer

When Oreskos Explorer enters, search your library for up to X Plains cards, where X is the number of players who control more lands than you. Reveal those cards, put them into your hand, then shuffle.

Elesh Norn, Mother of Machines

Vigilance
If a permanent entering causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.
Permanents entering don't cause abilities of permanents your opponents control to trigger.

Fledgling Griffin

Landfall — Whenever a land you control enters, Fledgling Griffin gains flying until end of turn.

Ondu Greathorn

First strike
Landfall — Whenever a land you control enters, Ondu Greathorn gets +2/+2 until end of turn.

Keeper of the Accord

At the beginning of each opponent's end step, if that player controls more creatures than you, create a 1/1 white Soldier creature token.
At the beginning of each opponent's end step, if that player controls more lands than you, you may search your library for a basic Plains card, put it onto the battlefield tapped, then shuffle.

Steppe Lynx

Landfall — Whenever a land you control enters, Steppe Lynx gets +2/+2 until end of turn.

Makindi Ox

Landfall — Whenever a land you control enters, tap target creature an opponent controls.

Archaeomancer's Map

When Archaeomancer's Map enters, search your library for up to two basic Plains cards, reveal them, put them into your hand, then shuffle.
Whenever a land an opponent controls enters, if that player controls more lands than you, you may put a land card from your hand onto the battlefield.

Fearless Fledgling

Landfall — Whenever a land you control enters, put a +1/+1 counter on Fearless Fledgling. It gains flying until end of turn.

Admonition Angel

Flying
Landfall — Whenever a land you control enters, you may exile target nonland permanent other than Admonition Angel.
When Admonition Angel leaves the battlefield, return all cards exiled with it to the battlefield under their owners' control.

Space Marine Scout

First strike, vigilance
Concealed Position — When Space Marine Scout enters, if an opponent controls more lands than you, you may search your library for a Plains card, put it onto the battlefield tapped, then shuffle.

Prowling Felidar

Vigilance
Landfall — Whenever a land you control enters, put a +1/+1 counter on Prowling Felidar.

Canyon Jerboa

Landfall — Whenever a land you control enters, creatures you control get +1/+1 until end of turn.

Trove Warden

Vigilance
Landfall — Whenever a land you control enters, exile target permanent card with mana value 3 or less from your graveyard.
When Trove Warden dies, put each permanent card exiled with it onto the battlefield under the control of that card's owner.

Emeria Shepherd

Flying
Landfall — Whenever a land you control enters, you may return target nonland permanent card from your graveyard to your hand. If that land is a Plains, you may return that nonland permanent card to the battlefield instead.

Emeria Angel

Flying
Landfall — Whenever a land you control enters, you may create a 1/1 white Bird creature token with flying.

Stoic Farmer

When Stoic Farmer enters, search your library for a basic Plains card and reveal it. If an opponent controls more lands than you, put it onto the battlefield tapped. Otherwise, put it into your hand. Then shuffle.
Foretell {1}{W} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)

Felidar Retreat

Landfall — Whenever a land you control enters, choose one —
• Create a 2/2 white Cat Beast creature token.
• Put a +1/+1 counter on each creature you control. Those creatures gain vigilance until end of turn.

Retreat to Emeria

Landfall — Whenever a land you control enters, choose one —
• Create a 1/1 white Kor Ally creature token.
• Creatures you control get +1/+1 until end of turn.

Scouting Hawk

Flying
Keen Sight — When Scouting Hawk enters, if an opponent controls more lands than you, search your library for a basic Plains card, put it onto the battlefield tapped, then shuffle.

Knight of the White Orchid

First strike
When Knight of the White Orchid enters, if an opponent controls more lands than you, you may search your library for a Plains card, put it onto the battlefield, then shuffle.

Cartographer's Hawk

Flying
When Cartographer's Hawk deals combat damage to a player who controls more lands than you, return it to its owner's hand. If you do, you may search your library for a Plains card, put it onto the battlefield tapped, then shuffle.