Den of the Bugbear

If you control two or more other lands, Den of the Bugbear enters tapped.
{T}: Add {R}.
{3}{R}: Until end of turn, Den of the Bugbear becomes a 3/2 red Goblin creature with "Whenever this creature attacks, create a 1/1 red Goblin creature token that's tapped and attacking." It's still a land.

Swans of Bryn Argoll

Flying
If a source would deal damage to Swans of Bryn Argoll, prevent that damage. The source's controller draws cards equal to the damage prevented this way.

Island

Wandering Fumarole

Wandering Fumarole enters tapped.
{T}: Add {U} or {R}.
{2}{U}{R}: Until end of turn, Wandering Fumarole becomes a 1/4 blue and red Elemental creature with "{0}: Switch this creature's power and toughness until end of turn." It's still a land.

Mana Leak

Counter target spell unless its controller pays {3}.

Steam Vents

({T}: Add {U} or {R}.)
As Steam Vents enters, you may pay 2 life. If you don't, it enters tapped.

Treasure Hunt

Reveal cards from the top of your library until you reveal a nonland card, then put all cards revealed this way into your hand.

Mountain

Day's Undoing

Each player shuffles their hand and graveyard into their library, then draws seven cards. If it's your turn, end the turn. (Exile all spells and abilities from the stack, including this card. Discard down to your maximum hand size. Damage wears off, and "this turn" and "until end of turn" effects end.)

Sphinx's Tutelage

Whenever you draw a card, target opponent mills two cards. If two nonland cards that share a color were milled this way, repeat this process.
{5}{U}: Draw a card, then discard a card.

Pyre of the World Tree

Discard a land card: Pyre of the World Tree deals 2 damage to any target.
Whenever you discard a land card, exile the top card of your library. You may play that card this turn.

Invasion of Kaldheim

(As a Siege enters, choose an opponent to protect it. You and others can attack it. When it's defeated, exile it, then cast it transformed.)
When Invasion of Kaldheim enters, exile all cards from your hand, then draw that many cards. Until the end of your next turn, you may play cards exiled this way.

Invasion of Kaldheim // Pyre of the World Tree

Lavaglide Pathway

Riverglide Pathway

Riverglide Pathway // Lavaglide Pathway

Hall of Storm Giants

If you control two or more other lands, Hall of Storm Giants enters tapped.
{T}: Add {U}.
{5}{U}: Until end of turn, Hall of Storm Giants becomes a 7/7 blue Giant creature with ward {3}. It's still a land. (Whenever it becomes the target of a spell or ability an opponent controls, counter it unless that player pays {3}.)

Seismic Assault

Discard a land card: Seismic Assault deals 2 damage to any target.

Molten Vortex

{R}, Discard a land card: Molten Vortex deals 2 damage to any target.

Frostboil Snarl

As Frostboil Snarl enters, you may reveal an Island or Mountain card from your hand. If you don't, Frostboil Snarl enters tapped.
{T}: Add {U} or {R}.

Spell Pierce

Counter target noncreature spell unless its controller pays {2}.

Shivan Reef

{T}: Add {C}.
{T}: Add {U} or {R}. Shivan Reef deals 1 damage to you.

Brotherhood's End

Choose one —
• Brotherhood's End deals 3 damage to each creature and each planeswalker.
• Destroy all artifacts with mana value 3 or less.

Laboratory Maniac

If you would draw a card while your library has no cards in it, you win the game instead.