Island

Captain Howler, Sea Scourge

Ward—{2}, Pay 2 life.
Whenever you discard one or more cards, target creature gets +2/+0 until end of turn for each card discarded this way. Whenever that creature deals combat damage to a player this turn, you draw a card.

Three Steps Ahead

Spree (Choose one or more additional costs.)
+ {1}{U} — Counter target spell.
+ {3} — Create a token that's a copy of target artifact or creature you control.
+ {2} — Draw two cards, then discard a card.

Riverpyre Verge

{T}: Add {R}.
{T}: Add {U}. Activate only if you control an Island or a Mountain.

Mountain

Demand Answers

As an additional cost to cast this spell, sacrifice an artifact or discard a card.
Draw two cards.

Tersa Lightshatter

Haste
When Tersa Lightshatter enters, discard up to two cards, then draw that many cards.
Whenever Tersa Lightshatter attacks, if there are seven or more cards in your graveyard, exile a card at random from your graveyard. You may play that card this turn.

Restless Spire

This land enters tapped.
{T}: Add {U} or {R}.
{U}{R}: Until end of turn, this land becomes a 2/1 blue and red Elemental creature with "During your turn, this creature has first strike." It's still a land.
Whenever this land attacks, scry 1.

Shivan Reef

{T}: Add {C}.
{T}: Add {U} or {R}. This land deals 1 damage to you.

Marauding Mako

Whenever you discard one or more cards, put that many +1/+1 counters on this creature.
Cycling {2} ({2}, Discard this card: Draw a card.)

Fear of Missing Out

When this creature enters, discard a card, then draw a card.
Delirium — Whenever this creature attacks for the first time each turn, if there are four or more card types among cards in your graveyard, untap target creature. After this phase, there is an additional combat phase.

Monument to Endurance

Whenever you discard a card, choose one that hasn't been chosen this turn —
• Draw a card.
• Create a Treasure token.
• Each opponent loses 3 life.

Focus the Mind

This spell costs {2} less to cast if you've cast another spell this turn.
Draw three cards, then discard a card.

Glacial Dragonhunt

Draw a card, then you may discard a card. When you discard a nonland card this way, Glacial Dragonhunt deals 3 damage to target creature.
Harmonize {4}{U}{R} (You may cast this card from your graveyard for its harmonize cost. You may tap a creature you control to reduce that cost by {X}, where X is its power. Then exile this spell.)

Inti, Seneschal of the Sun

Whenever you attack, you may discard a card. When you do, put a +1/+1 counter on target attacking creature. It gains trample until end of turn.
Whenever you discard one or more cards, exile the top card of your library. You may play that card until your next end step.

Spirebluff Canal

This land enters tapped unless you control two or fewer other lands.
{T}: Add {U} or {R}.