Deep Gnome Terramancer

Flash
Mold Earth — Whenever one or more lands enter under an opponent's control without being played, you may search your library for a Plains card, put it onto the battlefield tapped, then shuffle. Do this only once each turn.

Settle the Wreckage

Exile all attacking creatures target player controls. That player may search their library for that many basic land cards, put those cards onto the battlefield tapped, then shuffle.

Tunnel Ignus

Whenever a land enters under an opponent's control, if that player had another land enter the battlefield under their control this turn, this creature deals 3 damage to that player.

Wilderness Elemental

Trample
Wilderness Elemental's power is equal to the number of nonbasic lands your opponents control.

New Frontiers

Each player may search their library for up to X basic land cards and put them onto the battlefield tapped. Then each player who searched their library this way shuffles.

Smuggler's Share

At the beginning of each end step, draw a card for each opponent who drew two or more cards this turn, then create a Treasure token for each opponent who had two or more lands enter the battlefield under their control this turn.

Mercadia's Downfall

Each attacking creature gets +1/+0 until end of turn for each nonbasic land defending player controls.

Primal Order

At the beginning of each player's upkeep, this enchantment deals damage to that player equal to the number of nonbasic lands they control.

Acidic Soil

Acidic Soil deals damage to each player equal to the number of lands they control.

Treacherous Terrain

Treacherous Terrain deals damage to each opponent equal to the number of lands that player controls.
Basic landcycling {2} ({2}, Discard this card: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.)

Cleansing

For each land, destroy that land unless any player pays 1 life.

Path to Exile

Exile target creature. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Jungle Wayfinder

When this creature enters, each player may search their library for a basic land card, reveal it, put it into their hand, then shuffle.

Veteran Explorer

When this creature dies, each player may search their library for up to two basic land cards, put them onto the battlefield, then shuffle.

Avatar of Growth

This spell costs {1} less to cast for each opponent you have.
Trample
When this creature enters, each player searches their library for up to two basic land cards, puts them onto the battlefield, then shuffles.

Tempt with Discovery

Tempting offer — Search your library for a land card and put it onto the battlefield. Each opponent may search their library for a land card and put it onto the battlefield. For each opponent who searches a library this way, search your library for a land card and put it onto the battlefield. Then each player who searched a library this way shuffles.

Weight of Spires

Weight of Spires deals damage to target creature equal to the number of nonbasic lands that creature's controller controls.

Price of Progress

Price of Progress deals damage to each player equal to twice the number of nonbasic lands that player controls.

Shattered Angel

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

Archaeomancer's Map

When this artifact 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.

Coastline Marauders

Trample
Whenever this creature attacks, it gets +1/+0 until end of turn for each land defending player controls.
Encore {4}{R}{R} ({4}{R}{R}, Exile this card from your graveyard: For each opponent, create a token copy that attacks that opponent this turn if able. They gain haste. Sacrifice them at the beginning of the next end step. Activate only as a sorcery.)

Pir's Whim

For each player, choose friend or foe. Each friend searches their library for a land card, puts it onto the battlefield tapped, then shuffles. Each foe sacrifices an artifact or enchantment of their choice.

Rootweaver Druid

When this creature enters, each opponent may search their library for up to three basic land cards. They each put one of those cards onto the battlefield tapped under your control and the rest onto the battlefield tapped under their control. Then each player who searched their library this way shuffles.