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.

Opposition Agent

Flash
You control your opponents while they're searching their libraries.
While an opponent is searching their library, they exile each card they find. You may play those cards for as long as they remain exiled, and you may spend mana as though it were mana of any color to cast them.

Ocelot Pride

First strike, lifelink
Ascend (If you control ten or more permanents, you get the city's blessing for the rest of the game.)
At the beginning of your end step, if you gained life this turn, create a 1/1 white Cat creature token. Then if you have the city's blessing, for each token you control that entered this turn, create a token that's a copy of it.

Archivist of Oghma

Flash
Whenever an opponent searches their library, you gain 1 life and draw a card.

Erode

Destroy target creature or planeswalker. Its controller may search their library for a basic land card, put it onto the battlefield tapped, then shuffle.

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.

Leonin Arbiter

Players can't search libraries. Any player may pay {2} for that player to ignore this effect until end of turn.

Ghost Quarter

{T}: Add {C}.
{T}, Sacrifice this land: Destroy target land. Its controller may search their library for a basic land card, put it onto the battlefield, then shuffle.