Stormtide Leviathan

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
All lands are Islands in addition to their other types.
Creatures without flying or islandwalk can't attack.

Mana Breach

Whenever a player casts a spell, that player returns a land they control to its owner's hand.

Tideforce Elemental

{U}, {T}: You may tap or untap another target creature.
Landfall — Whenever a land you control enters, you may untap Tideforce Elemental.

Soratami Cloudskater

Flying
{2}, Return a land you control to its owner's hand: Draw a card, then discard a card.

Ruin Crab

Landfall — Whenever a land you control enters, each opponent mills three cards. (To mill a card, a player puts the top card of their library into their graveyard.)

Tiller Engine

Whenever a land you control enters tapped, choose one —
• Untap that land.
• Tap target nonland permanent an opponent controls.

Patron of the Moon

Moonfolk offering (You may cast this spell any time you could cast an instant by sacrificing a Moonfolk and paying the difference in mana costs between this and the sacrificed Moonfolk. Mana cost includes color.)
Flying
{1}: Put up to two land cards from your hand onto the battlefield tapped.

Back to Basics

Nonbasic lands don't untap during their controllers' untap steps.

Myojin of Seeing Winds

Myojin of Seeing Winds enters with a divinity counter on it if you cast it from your hand.
Myojin of Seeing Winds has indestructible as long as it has a divinity counter on it.
Remove a divinity counter from Myojin of Seeing Winds: Draw a card for each permanent you control.

Soratami Seer

Flying
{4}, Return two lands you control to their owner's hand: Discard all the cards in your hand, then draw that many cards.

Scourge of Fleets

When Scourge of Fleets enters, return each creature your opponents control with toughness X or less to its owner's hand, where X is the number of Islands you control.

Seer's Sundial

Landfall — Whenever a land you control enters, you may pay {2}. If you do, draw a card.

Thwart

You may return three Islands you control to their owner's hand rather than pay this spell's mana cost.
Counter target spell.

Walking Atlas

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

Misleading Signpost

Flash
When Misleading Signpost enters during the declare attackers step, you may reselect which player or permanent target attacking creature is attacking. (It can't attack its controller or their permanents.)
{T}: Add {U}.

Windrider Eel

Flying
Landfall — Whenever a land you control enters, Windrider Eel gets +2/+2 until end of turn.

Soramaro, First to Dream

Flying
Soramaro, First to Dream's power and toughness are each equal to the number of cards in your hand.
{4}, Return a land you control to its owner's hand: Draw a card.

Trade Routes

{1}: Return target land you control to its owner's hand.
{1}, Discard a land card: Draw a card.

Icebreaker Kraken

This spell costs {1} less to cast for each snow land you control.
When Icebreaker Kraken enters, artifacts and creatures target opponent controls don't untap during that player's next untap step.
Return three snow lands you control to their owner's hand: Return Icebreaker Kraken to its owner's hand.

Trench Behemoth

Return a land you control to its owner's hand: Untap Trench Behemoth. It gains hexproof until end of turn.
Landfall — Whenever a land you control enters, target creature an opponent controls attacks during its controller's next combat phase if able.

Soratami Mirror-Mage

Flying
{3}, Return three lands you control to their owner's hand: Return target creature to its owner's hand.

Khalni Gem

When Khalni Gem enters, return two lands you control to their owner's hand.
{T}: Add two mana of any one color.

Adventuring Gear

Landfall — Whenever a land you control enters, equipped creature gets +2/+2 until end of turn.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Engulf the Shore

Return to their owners' hands all creatures with toughness less than or equal to the number of Islands you control.

Floodbringer

Flying
{2}, Return a land you control to its owner's hand: Tap target land.

Archmage's Charm

Choose one —
• Counter target spell.
• Target player draws two cards.
• Gain control of target nonland permanent with mana value 1 or less.

Storm Cauldron

Each player may play an additional land during each of their turns.
Whenever a land is tapped for mana, return it to its owner's hand.

Marit Lage's Slumber

Whenever Marit Lage's Slumber or another snow permanent you control enters, scry 1.
At the beginning of your upkeep, if you control ten or more snow permanents, sacrifice Marit Lage's Slumber. If you do, create Marit Lage, a legendary 20/20 black Avatar creature token with flying and indestructible.

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.)

Gush

You may return two Islands you control to their owner's hand rather than pay this spell's mana cost.
Draw two cards.

Kefnet the Mindful

Flying, indestructible
Kefnet the Mindful can't attack or block unless you have seven or more cards in hand.
{3}{U}: Draw a card, then you may return a land you control to its owner's hand.

Flow of Ideas

Sunder

Ovinomancer

When Ovinomancer enters, sacrifice it unless you return three basic lands you control to their owner's hand.
{T}, Return Ovinomancer to its owner's hand: Destroy target creature. It can't be regenerated. That creature's controller creates a 0/1 green Sheep creature token.

Thran Dynamo

Whir of Invention

Improvise (Your artifacts can help cast this spell. Each artifact you tap after you're done activating mana abilities pays for {1}.)
Search your library for an artifact card with mana value X or less, put it onto the battlefield, then shuffle.

Soratami Rainshaper

Flying
{3}, Return a land you control to its owner's hand: Target creature you control gains shroud until end of turn. (It can't be the target of spells or abilities.)

Spectral Deluge

Return each creature your opponents control with toughness X or less to its owner's hand, where X is the number of Islands you control.
Foretell {1}{U}{U} (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.)

Soratami Mirror-Guard

Flying
{2}, Return a land you control to its owner's hand: Target creature with power 2 or less can't be blocked this turn.

Snow-Covered Island

Locus of Enlightenment

Locus of Enlightenment has each activated ability of the exiled cards used to craft it. You may activate each of those abilities only once each turn.
Whenever you activate an ability that isn't a mana ability, copy it. You may choose new targets for the copy.

The Enigma Jewel

The Enigma Jewel enters tapped.
{T}: Add {C}{C}. Spend this mana only to activate abilities.
Craft with four or more nonlands with activated abilities {8}{U} ({8}{U}, Exile this artifact, Exile the four or more from among other permanents you control and/or cards in your graveyard: Return this card transformed under its owner's control. Craft only as a sorcery.)

The Enigma Jewel // Locus of Enlightenment

Sceptre of Eternal Glory

{T}: Add one mana of any color.
{T}: Add three mana of any one color. Activate only if you control three or more lands with the same name.

Scaretiller

Whenever Scaretiller becomes tapped, choose one —
• You may put a land card from your hand onto the battlefield tapped.
• Return target land card from your graveyard to the battlefield tapped.

Amulet of Vigor

Whenever a permanent you control enters tapped, untap it.

Roil Elemental

Flying
Landfall — Whenever a land you control enters, you may gain control of target creature for as long as you control Roil Elemental.

Overburden

Whenever a player puts a nontoken creature onto the battlefield, that player returns a land they control to its owner's hand.

Flooded Shoreline

{U}{U}, Return two Islands you control to their owner's hand: Return target creature to its owner's hand.

High Tide

Until end of turn, whenever a player taps an Island for mana, that player adds an additional {U}.

Fathom Seer

Morph—Return two Islands you control to their owner's hand. (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)
When Fathom Seer is turned face up, draw two cards.

Meloku the Clouded Mirror

Flying
{1}, Return a land you control to its owner's hand: Create a 1/1 blue Illusion creature token with flying.

Oboro Breezecaller

Flying
{2}, Return a land you control to its owner's hand: Untap target land.

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.

Omen Hawker

{T}: Add {C}{U}. Spend this mana only to activate abilities.

Uyo, Silent Prophet

Flying
{2}, Return two lands you control to their owner's hand: Copy target instant or sorcery spell. You may choose new targets for the copy.

Oboro Envoy

Flying
{2}, Return a land you control to its owner's hand: Target creature gets -X/-0 until end of turn, where X is the number of cards in your hand.

Soratami Savant

Flying
{3}, Return a land you control to its owner's hand: Counter target spell unless its controller pays {3}.

Ensnare

You may return two Islands you control to their owner's hand rather than pay this spell's mana cost.
Tap all creatures.

Aetherspouts

For each attacking creature, its owner puts it on their choice of the top or bottom of their library.

Blackblade Reforged

Equipped creature gets +1/+1 for each land you control.
Equip legendary creature {3}
Equip {7}