Harbinger of the Seas

Grindstone

{3}, {T}: Target player mills two cards. If two cards that share a color were milled this way, repeat this process.

Hydroblast

Choose one —
• Counter target spell if it's red.
• Destroy target permanent if it's red.

Sway of Illusion

Any number of target creatures become the color of your choice until end of turn.
Draw a card.

Well-Laid Plans

Prevent all damage that would be dealt to a creature by another creature if they share a color.

Alter Reality

Change the text of target spell or permanent by replacing all instances of one color word with another. (This effect lasts indefinitely.)
Flashback {1}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Arcane Denial

Counter target spell. Its controller may draw up to two cards at the beginning of the next turn's upkeep.
You draw a card at the beginning of the next turn's upkeep.

Fabricate

Search your library for an artifact card, reveal it, put it into your hand, then shuffle.

Training Grounds

Activated abilities of creatures you control cost {2} less to activate. This effect can't reduce the mana in that cost to less than one mana.

Tidal Control

Cumulative upkeep {2} (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
Pay 2 life or {2}: Counter target red or green spell. Any player may activate this ability.

Blue Elemental Blast

Choose one —
• Counter target red spell.
• Destroy target red permanent.

Flash Flood

Choose one —
• Destroy target red permanent.
• Return target Mountain to its owner's hand.

Distorting Lens

{T}: Target permanent becomes the color of your choice until end of turn.

Cowardice

Whenever a creature becomes the target of a spell or ability, return that creature to its owner's hand. (It won't be affected by the spell or ability.)

Blind Seer

{1}{U}: Target spell or permanent becomes the color of your choice until end of turn.

Shifting Sky

As Shifting Sky enters, choose a color.
All nonland permanents are the chosen color.

Archmage Emeritus

Magecraft — Whenever you cast or copy an instant or sorcery spell, draw a card.

Dismiss into Dream

Each creature your opponents control is an Illusion in addition to its other types and has "When this creature becomes the target of a spell or ability, sacrifice it."

Insight

Whenever an opponent casts a green spell, you draw a card.

Painter's Servant

As Painter's Servant enters, choose a color.
All cards that aren't on the battlefield, spells, and permanents are the chosen color in addition to their other colors.

Case of the Shattered Pact

When this Case enters, search your library for a basic land card, reveal it, put it into your hand, then shuffle.
To solve — There are five colors among permanents you control. (If unsolved, solve at the beginning of your end step.)
Solved — At the beginning of combat on your turn, target creature you control gains flying, double strike, and vigilance until end of turn.

Willbreaker

Whenever a creature an opponent controls becomes the target of a spell or ability you control, gain control of that creature for as long as you control Willbreaker.

Douse

Sapphire Medallion

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

Thought Vessel

You have no maximum hand size.
{T}: Add {C}.

Wash Out

Return all permanents of the color of your choice to their owners' hands.

Heartstone

Activated abilities of creatures cost {1} less to activate. This effect can't reduce the mana in that cost to less than one mana.