Staff of the Ages

Creatures with landwalk abilities can be blocked as though they didn't have those abilities.

Cave Sense

Enchant creature
Enchanted creature gets +1/+1 and has mountainwalk. (It can't be blocked as long as defending player controls a Mountain.)

Bog Tatters

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)

Snow-Covered Swamp

Goblin King

Other Goblins get +1/+1 and have mountainwalk.

Shimmer

As Shimmer enters, choose a land type.
Each land of the chosen type has phasing. (It phases in or out before its controller untaps during each of their untap steps. While it's phased out, it's treated as though it doesn't exist.)

Stonybrook Banneret

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Merfolk spells and Wizard spells you cast cost {1} less to cast.

Fishliver Oil

Enchant creature (Target a creature as you cast this. This card enters attached to that creature.)
Enchanted creature has islandwalk. (It can't be blocked as long as defending player controls an Island.)

Volcanic Strength

Enchant creature
Enchanted creature gets +2/+2 and has mountainwalk. (It can't be blocked as long as defending player controls a Mountain.)

Merfolk Spy

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Whenever Merfolk Spy deals combat damage to a player, that player reveals a card at random from their hand.

Legions of Lim-Dûl

Snow swampwalk (This creature can't be blocked as long as defending player controls a snow Swamp.)

Burrowing

Enchant creature
Enchanted creature has mountainwalk. (It can't be blocked as long as defending player controls a Mountain.)

Boggart Arsonists

Plainswalk (This creature can't be blocked as long as defending player controls a Plains.)
{2}{R}, Sacrifice Boggart Arsonists: Destroy target Scarecrow or Plains.

Koth's Courier

Forestwalk (This creature can't be blocked as long as defending player controls a Forest.)

Blistergrub

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
When Blistergrub dies, each opponent loses 2 life.

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.

Magical Hack

Change the text of target spell or permanent by replacing all instances of one basic land type with another. (For example, you may change "swampwalk" to "plainswalk." This effect lasts indefinitely.)

Orcish Farmer

{T}: Target land becomes a Swamp until its controller's next untap step.

Mountain

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Defile

Target creature gets -1/-1 until end of turn for each Swamp you control.

Blanket of Night

Each land is a Swamp in addition to its other land types.

Evil Presence

Melting

Goblin Spelunkers

Mountainwalk (This creature can't be blocked as long as defending player controls a Mountain.)

Mind Bend

Change the text of target permanent by replacing all instances of one color word with another or one basic land type with another. (For example, you may change "nonblack creature" to "nongreen creature" or "forestwalk" to "islandwalk." This effect lasts indefinitely.)

Island

Merfolk Raiders

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Phasing (This phases in or out before you untap during each of your untap steps. While it's phased out, it's treated as though it doesn't exist.)

Goblins of the Flarg

Mountainwalk (This creature can't be blocked as long as defending player controls a Mountain.)
When you control a Dwarf, sacrifice Goblins of the Flarg.

Counterspell

Master of the Pearl Trident

Other Merfolk creatures you control get +1/+1 and have islandwalk. (They can't be blocked as long as defending player controls an Island.)

Cancel

Dwarven Grunt

Dissolve

Counter target spell. Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Marsh Goblins

Mystic Compass

{1}, {T}: Target land becomes the basic land type of your choice until end of turn.

Relic of Legends

{T}: Add one mana of any color.
Tap an untapped legendary creature you control: Add one mana of any color.

Mystic Decree

All creatures lose flying and islandwalk.

Sol'kanar the Swamp King

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
Whenever a player casts a black spell, you gain 1 life.

Rishadan Dockhand

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
{1}, {T}: Tap target land.

Dark Ritual

Slinking Serpent

Goblin Flotilla

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
At the beginning of each combat, unless you pay {R}, whenever Goblin Flotilla blocks or becomes blocked by a creature this combat, that creature gains first strike until end of turn.

Leshrac's Rite

Enchant creature
Enchanted creature has swampwalk. (It can't be blocked as long as defending player controls a Swamp.)

Snow-Covered Mountain

War Barge

{3}: Target creature gains islandwalk until end of turn. When War Barge leaves the battlefield this turn, destroy that creature. A creature destroyed this way can't be regenerated. (A creature with islandwalk can't be blocked as long as defending player controls an Island.)

Nightcreep

Until end of turn, all creatures become black and all lands become Swamps.

Sunder

Phantasmal Terrain

Enchant land
As Phantasmal Terrain enters, choose a basic land type.
Enchanted land is the chosen type.

Crevasse

Creatures with mountainwalk can be blocked as though they didn't have mountainwalk.

Taniwha

Trample
Phasing (This phases in or out before you untap during each of your untap steps. While it's phased out, it's treated as though it doesn't exist.)
At the beginning of your upkeep, all lands you control phase out. (They phase in before you untap during your next untap step.)

River Merfolk

{U}: River Merfolk gains mountainwalk until end of turn. (It can't be blocked as long as defending player controls a Mountain.)

Swamp

Sand Squid

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
You may choose not to untap Sand Squid during your untap step.
{T}: Tap target creature. That creature doesn't untap during its controller's untap step for as long as Sand Squid remains tapped.

Filth

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
As long as Filth is in your graveyard and you control a Swamp, creatures you control have swampwalk.

Boggart Loggers

Forestwalk (This creature can't be blocked as long as defending player controls a Forest.)
{2}{B}, Sacrifice Boggart Loggers: Destroy target Treefolk or Forest.

Streambed Aquitects

{T}: Target Merfolk creature gets +1/+1 and gains islandwalk until end of turn. (It can't be blocked as long as defending player controls an Island.)
{T}: Target land becomes an Island until end of turn.