Springleaf Drum

{T}, Tap an untapped creature you control: Add one mana of any color.

Conclave's Blessing

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.)
Enchant creature
Enchanted creature gets +0/+2 for each other creature you control.

Prismatic Strands

Prevent all damage that sources of the color of your choice would deal this turn.
Flashback—Tap an untapped white creature you control. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Samite Herbalist

Whenever Samite Herbalist becomes tapped, you gain 1 life and scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Palace Sentinels

When Palace Sentinels enters, you become the monarch.

Azorius Chancery

Azorius Chancery enters tapped.
When Azorius Chancery enters, return a land you control to its owner's hand.
{T}: Add {W}{U}.

Plains

Triplicate Spirits

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.)
Create three 1/1 white Spirit creature tokens with flying.

Vizier of Tumbling Sands

{T}: Untap another target permanent.
Cycling {1}{U} ({1}{U}, Discard this card: Draw a card.)
When you cycle Vizier of Tumbling Sands, untap target permanent.

Meeting of Minds

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.)
Draw two cards.

Island

Cut Short

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 target planeswalker that was activated this turn or tapped creature.

Stonybrook Schoolmaster

Whenever Stonybrook Schoolmaster becomes tapped, you may create a 1/1 blue Merfolk Wizard creature token.

Counterspell

Aradara Express

Menace
Crew 4 (Tap any number of creatures you control with total power 4 or more: This Vehicle becomes an artifact creature until end of turn.)

Nimbleclaw Adept

Bigby's Hand — {T}: Untap two other target permanents. Activate only as a sorcery and only once each turn.

Make Your Move

Destroy target artifact, enchantment, or creature with power 4 or greater.

Judge of Currents

Whenever a Merfolk you control becomes tapped, you may gain 1 life.

Annul

Counter target artifact or enchantment spell.

Ephemeral Shields

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.)
Target creature gains indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)