Nykthos, Shrine to Nyx

{T}: Add {C}.
{2}, {T}: Choose a color. Add an amount of mana of that color equal to your devotion to that color. (Your devotion to a color is the number of mana symbols of that color in the mana costs of permanents you control.)

Oketra's Monument

White creature spells you cast cost {1} less to cast.
Whenever you cast a creature spell, create a 1/1 white Warrior creature token with vigilance.

Dawn's Truce

Gift a card (You may promise an opponent a gift as you cast this spell. If you do, they draw a card before its other effects.)
You and permanents you control gain hexproof until end of turn. If the gift was promised, permanents you control also gain indestructible until end of turn.

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Pearl Medallion

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

Magus of the Moat

Momo, Friendly Flier

Flying
The first non-Lemur creature spell with flying you cast during each of your turns costs {1} less to cast.
Whenever another creature you control with flying enters, Momo gets +1/+1 until end of turn.

Sol Ring

Flare of Fortitude

You may sacrifice a nontoken white creature rather than pay this spell's mana cost.
Until end of turn, your life total can't change, and permanents you control gain hexproof and indestructible.

Tempest Hawk

Flying
Whenever this creature deals combat damage to a player, you may search your library for a card named Tempest Hawk, reveal it, put it into your hand, then shuffle.
A deck can have any number of cards named Tempest Hawk.