Teferi, Time Raveler

Each opponent can cast spells only any time they could cast a sorcery.
+1: Until your next turn, you may cast sorcery spells as though they had flash.
−3: Return up to one target artifact, creature, or enchantment to its owner's hand. Draw a card.

Breeding Pool

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

Omen of the Sea

Flash (You may cast this spell any time you could cast an instant.)
When Omen of the Sea enters, scry 2, then draw a card.
{2}{U}, Sacrifice Omen of the Sea: Scry 2. (Look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Island

Mystical Dispute

This spell costs {2} less to cast if it targets a blue spell.
Counter target spell unless its controller pays {3}.

Mana Leak

Counter target spell unless its controller pays {3}.

Summoner's Pact

Search your library for a green creature card, reveal it, put it into your hand, then shuffle.
At the beginning of your next upkeep, pay {2}{G}{G}. If you don't, you lose the game.

Remand

Counter target spell. If that spell is countered this way, put it into its owner's hand instead of into that player's graveyard.
Draw a card.

Glacial Fortress

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

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.

Temple Garden

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

Devoted Druid

{T}: Add {G}.
Put a -1/-1 counter on Devoted Druid: Untap Devoted Druid.

Serum Visions

Hallowed Fountain

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

Krallenhorde Howler

Creature spells you cast cost {1} less to cast.
At the beginning of each upkeep, if a player cast two or more spells last turn, transform Krallenhorde Howler.

Duskwatch Recruiter

{2}{G}: Look at the top three cards of your library. You may reveal a creature card from among them and put it into your hand. Put the rest on the bottom of your library in any order.
At the beginning of each upkeep, if no spells were cast last turn, transform Duskwatch Recruiter.

Duskwatch Recruiter // Krallenhorde Howler

Vizier of Remedies

If one or more -1/-1 counters would be put on a creature you control, that many -1/-1 counters minus one are put on it instead.

Walking Ballista

Walking Ballista enters with X +1/+1 counters on it.
{4}: Put a +1/+1 counter on Walking Ballista.
Remove a +1/+1 counter from Walking Ballista: It deals 1 damage to any target.

Noble Hierarch

Exalted (Whenever a creature you control attacks alone, that creature gets +1/+1 until end of turn.)
{T}: Add {G}, {W}, or {U}.

Sunpetal Grove

Sunpetal Grove enters tapped unless you control a Forest or a Plains.
{T}: Add {G} or {W}.

Windswept Heath

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