Sapphire Medallion

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

Sensei's Divining Top

{1}: Look at the top three cards of your library, then put them back in any order.
{T}: Draw a card, then put Sensei's Divining Top on top of its owner's library.

Explosion

Explosion deals X damage to any target. Target player draws X cards.

Expansion

Copy target instant or sorcery spell with mana value 4 or less. You may choose new targets for the copy.

Expansion // Explosion

Ruby Medallion

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

Lullmage Mentor

Whenever a spell or ability you control counters a spell, you may create a 1/1 blue Merfolk creature token.
Tap seven untapped Merfolk you control: Counter target spell.

Harbinger of the Seas

Powerbalance

Whenever an opponent casts a spell, you may reveal the top card of your library. If you do, you may cast that card without paying its mana cost if the two spells have the same mana value.

Counterbalance

Whenever an opponent casts a spell, you may reveal the top card of your library. If you do, counter that spell if it has the same mana value as the revealed card.

Cooperate

Aftermath (Cast this spell only from your graveyard. Then exile it.)
Copy target instant or sorcery spell. You may choose new targets for the copy.

Refuse

Refuse deals damage to target spell's controller equal to that spell's mana value.

Refuse // Cooperate

Counterspell

Brainsurge

Draw four cards, then put two cards from your hand on top of your library in any order.

Ral, Storm Conduit

Whenever you cast or copy an instant or sorcery spell, Ral, Storm Conduit deals 1 damage to target opponent or planeswalker.
+2: Scry 1.
−2: When you next cast an instant or sorcery spell this turn, copy that spell. You may choose new targets for the copy.