Spell Queller

Flash
Flying
When Spell Queller enters, exile target spell with mana value 4 or less.
When Spell Queller leaves the battlefield, the exiled card's owner may cast that card without paying its mana cost.

Hallowed Fountain

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

Port Town

As Port Town enters, you may reveal a Plains or Island card from your hand. If you don't, Port Town enters tapped.
{T}: Add {W} or {U}.

Restoration Angel

Flash
Flying
When Restoration Angel enters, you may exile target non-Angel creature you control, then return that card to the battlefield under your control.

Glacial Fortress

Glacial Fortress enters tapped unless you control a Plains or an Island.
{T}: Add {W} or {U}.

Master of Waves

Protection from red
Elemental creatures you control get +1/+1.
When Master of Waves enters, create a number of 1/0 blue Elemental creature tokens equal to your devotion to blue. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)

Venser, the Sojourner

+2: Exile target permanent you own. Return it to the battlefield under your control at the beginning of the next end step.
−1: Creatures can't be blocked this turn.
−8: You get an emblem with "Whenever you cast a spell, exile target permanent."

Plains

Flooded Strand

{T}, Pay 1 life, Sacrifice Flooded Strand: Search your library for a Plains or Island card, put it onto the battlefield, then shuffle.

Naban, Dean of Iteration

If a Wizard entering under your control causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Island

Reflector Mage

When Reflector Mage enters, return target creature an opponent controls to its owner's hand. That creature's owner can't cast spells with the same name as that creature until your next turn.

Venser, Shaper Savant

Flash
When Venser, Shaper Savant enters, return target spell or permanent to its owner's hand.

Meddling Mage

As Meddling Mage enters, choose a nonland card name.
Spells with the chosen name can't be cast.

Path to Exile

Exile target creature. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.