Shoal Serpent

Defender
Landfall — Whenever a land you control enters, Shoal Serpent loses defender until end of turn.

Command of Unsummoning

Cast this spell only during the declare attackers step and only if you've been attacked this step.
Return one or two target attacking creatures to their owner's hand.

Maze of Ith

{T}: Untap target attacking creature. Prevent all combat damage that would be dealt to and dealt by that creature this turn.

Walking Atlas

{T}: You may put a land card from your hand onto the battlefield.

Mystic Remora

Cumulative upkeep {1} (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
Whenever an opponent casts a noncreature spell, you may draw a card unless that player pays {4}.

Embodiment of Fury

Trample
Land creatures you control have trample.
Landfall — Whenever a land you control enters, you may have target land you control become a 3/3 Elemental creature with haste until end of turn. It's still a land.

Cosi's Ravager

Landfall — Whenever a land you control enters, you may have Cosi's Ravager deal 1 damage to target player or planeswalker.

Counterspell

Guardian of Tazeem

Flying
Landfall — Whenever a land you control enters, tap target creature an opponent controls. If that land is an Island, that creature doesn't untap during its controller's next untap step.

Semblance Anvil

Imprint — When Semblance Anvil enters, you may exile a nonland card from your hand.
Spells you cast that share a card type with the exiled card cost {2} less to cast.

Unsummon

Return target creature to its owner's hand.

Sol Ring

Zektar Shrine Expedition

Landfall — Whenever a land you control enters, you may put a quest counter on Zektar Shrine Expedition.
Remove three quest counters from Zektar Shrine Expedition and sacrifice it: Create a 7/1 red Elemental creature token with trample and haste. Exile it at the beginning of the next end step.

Izzet Signet

Nesting Dragon

Flying
Landfall — Whenever a land you control enters, create a 0/2 red Dragon Egg creature token with defender and "When this creature dies, create a 2/2 red Dragon creature token with flying and '{R}: This creature gets +1/+0 until end of turn.'"

Crucible of Worlds

Panoptic Mirror

Imprint — {X}, {T}: You may exile an instant or sorcery card with mana value X from your hand.
At the beginning of your upkeep, you may copy a card exiled with Panoptic Mirror. If you do, you may cast the copy without paying its mana cost.

Retreat to Coralhelm

Landfall — Whenever a land you control enters, choose one —
• You may tap or untap target creature.
• Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Calcite Snapper

Shroud (This creature can't be the target of spells or abilities.)
Landfall — Whenever a land you control enters, you may switch Calcite Snapper's power and toughness until end of turn.

Boil

Searing Blaze

Searing Blaze deals 1 damage to target player or planeswalker and 1 damage to target creature that player or that planeswalker's controller controls.
Landfall — If you had a land enter the battlefield under your control this turn, Searing Blaze deals 3 damage to that player or planeswalker and 3 damage to that creature instead.

Island

Akoum Hellhound

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

Ior Ruin Expedition

Landfall — Whenever a land you control enters, you may put a quest counter on Ior Ruin Expedition.
Remove three quest counters from Ior Ruin Expedition and sacrifice it: Draw two cards.