Urza's Incubator

As Urza's Incubator enters, choose a creature type.
Creature spells of the chosen type cost {2} less to cast.

Root Maze

Ruby Medallion

Red spells you cast cost {1} less to cast.

Boseiju, Who Shelters All

Boseiju, Who Shelters All enters tapped.
{T}, Pay 2 life: Add {C}. If that mana is spent on an instant or sorcery spell, that spell can't be countered.

Silence

Your opponents can't cast spells this turn.

Sanctum of Eternity

{T}: Add {C}.
{2}, {T}: Return target commander you own from the battlefield to your hand. Activate only during your turn.

Prairie Stream

({T}: Add {W} or {U}.)
Prairie Stream enters tapped unless you control two or more basic lands.

Force of Will

You may pay 1 life and exile a blue card from your hand rather than pay this spell's mana cost.
Counter target spell.

Mystic Gate

{T}: Add {C}.
{W/U}, {T}: Add {W}{W}, {W}{U}, or {U}{U}.

Sea of Clouds

Sea of Clouds enters tapped unless you have two or more opponents.
{T}: Add {W} or {U}.

Teferi's Protection

Until your next turn, your life total can't change and you gain protection from everything. All permanents you control phase out. (While they're phased out, they're treated as though they don't exist. They phase in before you untap during your untap step.)
Exile Teferi's Protection.

Heliod, the Warped Eclipse

You may cast spells as though they had flash.
Spells you cast cost {1} less to cast for each card your opponents have drawn this turn.

Heliod, the Radiant Dawn

When Heliod, the Radiant Dawn enters, return target enchantment card that isn't a God from your graveyard to your hand.
{3}{U/P}: Transform Heliod, the Radiant Dawn. Activate only as a sorcery. ({U/P} can be paid with either {U} or 2 life.)

Heliod, the Radiant Dawn // Heliod, the Warped Eclipse

Rule of Law

Each player can't cast more than one spell each turn.

Entomb

Search your library for a card, put that card into your graveyard, then shuffle.