Have

Mana Leak

Counter target spell unless its controller pays {3}.

Getting

Lightning Strike

Lightning Strike deals 3 damage to any target.

Stymied Hopes

Counter target spell unless its controller pays {1}. Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Spark Jolt

Spark Jolt deals 1 damage to any target. Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Clout of the Dominus

Enchant creature
As long as enchanted creature is blue, it gets +1/+1 and has shroud. (It can't be the target of spells or abilities.)
As long as enchanted creature is red, it gets +1/+1 and has haste.

Tyrannize

Target player discards their hand unless they pay 7 life.

Stern Dismissal

Return target creature or enchantment an opponent controls to its owner's hand.

Twisted Image

Switch target creature's power and toughness until end of turn.
Draw a card.

Spectral Sailor

Flash (You may cast this spell any time you could cast an instant.)
Flying
{3}{U}: Draw a card.

Mountain

Nivmagus Elemental

Exile an instant or sorcery spell you control: Put two +1/+1 counters on this creature. (That spell won't resolve.)

Scry 1. (Look at the top card of your library. You may put that card on the bottom.)
Draw a card.

Gleaming Geardrake

Flying
When this creature enters, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")
Whenever you sacrifice an artifact, put a +1/+1 counter on this creature.

Talrand, Sky Summoner

Whenever you cast an instant or sorcery spell, create a 2/2 blue Drake creature token with flying.

Young Pyromancer

Whenever you cast an instant or sorcery spell, create a 1/1 red Elemental creature token.

Divination

Aerial Formation

Strive — This spell costs {2}{U} more to cast for each target beyond the first.
Any number of target creatures each get +1/+1 and gain flying until end of turn.

Staff of the Mind Magus

Whenever you cast a blue spell or an Island you control enters, you gain 1 life.

Frost Walker

When this creature becomes the target of a spell or ability, sacrifice it.

Bountiful Landscape

{T}: Add {C}.
{T}, Sacrifice this land: Search your library for a basic Forest, Island, or Mountain card, put it onto the battlefield tapped, then shuffle.
Cycling {G}{U}{R} ({G}{U}{R}, Discard this card: Draw a card.)

Scion of Glaciers

{U}: This creature gets +1/-1 until end of turn.

Aether Spellbomb

{U}, Sacrifice this artifact: Return target creature to its owner's hand.
{1}, Sacrifice this artifact: Draw a card.

Island

Involuntary Employment

Gain control of target creature until end of turn. Untap that creature. It gains haste until end of turn. Create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Scaldkin

Flying
{2}{R}, Sacrifice this creature: It deals 2 damage to any target.

Steamcore Weird

When this creature enters, if {R} was spent to cast it, it deals 2 damage to any target.

Repeal

Return target nonland permanent with mana value X to its owner's hand.
Draw a card.

Shock

Swiftwater Cliffs

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {U} or {R}.

Spell Pierce

Counter target noncreature spell unless its controller pays {2}.

LOTR

Gandalf the Grey

Whenever you cast an instant or sorcery spell, choose one that hasn't been chosen —
• You may tap or untap target permanent.
• Gandalf deals 3 damage to each opponent.
• Copy target instant or sorcery spell you control. You may choose new targets for the copy.
• Put Gandalf on top of its owner's library.

Lava Coil

Lava Coil deals 4 damage to target creature. If that creature would die this turn, exile it instead.