Mystic Monastery

Mystic Monastery enters tapped.
{T}: Add {U}, {R}, or {W}.

Command Tower

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

Exotic Orchard

{T}: Add one mana of any color that a land an opponent controls could produce.

Arcane Signet

Saint Traft and Rem Karolus

Whenever Saint Traft and Rem Karolus becomes tapped, create a 1/1 red Human creature token if this is the first time this ability has resolved this turn. If it's the second time, create a 1/1 blue Spirit creature token with flying. If it's the third time, create a 4/4 white Angel creature token with flying.
Whenever you cast a spell that has convoke, untap Saint Traft and Rem Karolus.

Prairie Stream

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

Kasla, the Broken Halo

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Flying, vigilance, haste
Whenever you cast another spell that has convoke, scry 2, then draw a card.

Boros Signet

Kykar, Wind's Fury

Flying
Whenever you cast a noncreature spell, create a 1/1 white Spirit creature token with flying.
Sacrifice a Spirit: Add {R}.

Izzet Signet

Hour of Reckoning

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Destroy all nontoken creatures.

Impact Tremors

Whenever a creature you control enters, Impact Tremors deals 1 damage to each opponent.

Jeskai Ascendancy

Whenever you cast a noncreature spell, creatures you control get +1/+1 until end of turn. Untap those creatures.
Whenever you cast a noncreature spell, you may draw a card. If you do, discard a card.