Big Score

As an additional cost to cast this spell, discard a card.
Draw two cards and create two Treasure tokens. (They're artifacts with "{T}, Sacrifice this artifact: Add one mana of any color.")

Mountain

One with the Multiverse

You may look at the top card of your library any time.
You may play lands and cast spells from the top of your library.
Once during each of your turns, you may cast a spell from your hand or the top of your library without paying its mana cost.

Stormcarved Coast

Stormcarved Coast enters tapped unless you control two or more other lands.
{T}: Add {U} or {R}.

Yavimaya Coast

{T}: Add {C}.
{T}: Add {G} or {U}. Yavimaya Coast deals 1 damage to you.

Genesis Ultimatum

Look at the top five cards of your library. Put any number of permanent cards from among them onto the battlefield and the rest into your hand. Exile Genesis Ultimatum.

Crackle with Power

Crackle with Power deals five times X damage to each of up to X targets.

Third Path Iconoclast

Whenever you cast a noncreature spell, create a 1/1 colorless Soldier artifact creature token.

Storm King's Thunder

When you next cast an instant or sorcery spell this turn, copy that spell X times. You may choose new targets for the copies.

Growth Spiral

Draw a card. You may put a land card from your hand onto the battlefield.

Steam Vents

({T}: Add {U} or {R}.)
As Steam Vents enters, you may pay 2 life. If you don't, it enters tapped.

Arena of Glory

Arena of Glory enters tapped unless you control a Mountain.
{T}: Add {R}.
{R}, {T}, Exert Arena of Glory: Add {R}{R}. If that mana is spent on a creature spell, it gains haste until end of turn. (An exerted permanent won't untap during your next untap step.)

Archmage of Runes

Instant and sorcery spells you cast cost {1} less to cast.
Whenever you cast an instant or sorcery spell, draw a card.

Saheeli, Sublime Artificer

Whenever you cast a noncreature spell, create a 1/1 colorless Servo artifact creature token.
−2: Target artifact you control becomes a copy of another target artifact or creature you control until end of turn, except it's an artifact in addition to its other types.

Tasha's Hideous Laughter

Each opponent exiles cards from the top of their library until that player has exiled cards with total mana value 20 or more.

Expressive Iteration

Look at the top three cards of your library. Put one of them into your hand, put one of them on the bottom of your library, and exile one of them. You may play the exiled card this turn.

Shivan Reef

{T}: Add {C}.
{T}: Add {U} or {R}. Shivan Reef deals 1 damage to you.

Baral, Chief of Compliance

Instant and sorcery spells you cast cost {1} less to cast.
Whenever a spell or ability you control counters a spell, you may draw a card. If you do, discard a card.

Consider

Surveil 1. (Look at the top card of your library. You may put it into your graveyard.)
Draw a card.

Island

Rampant Growth

Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Dreamroot Cascade

Dreamroot Cascade enters tapped unless you control two or more other lands.
{T}: Add {G} or {U}.

Enter the Enigma

Target creature can't be blocked this turn.
Draw a card.

Blood Mist

At the beginning of combat on your turn, target creature you control gains double strike until end of turn.

Hinterland Harbor

Hinterland Harbor enters tapped unless you control a Forest or an Island.
{T}: Add {G} or {U}.

Stormcatch Mentor

Haste
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Instant and sorcery spells you cast cost {1} less to cast.

Chaos Warp

The owner of target permanent shuffles it into their library, then reveals the top card of their library. If it's a permanent card, they put it onto the battlefield.

Young Pyromancer

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

Ketria Triome

({T}: Add {G}, {U}, or {R}.)
Ketria Triome enters tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)

Storm, Force of Nature

Flying, vigilance
Ceaseless Tempest — Whenever Storm deals combat damage to a player, the next instant or sorcery spell you cast this turn has storm. (When you cast it, copy it for each spell cast before it this turn. You may choose new targets for the copies.)

Forest

Irenicus's Vile Duplication

Create a token that's a copy of target creature you control, except the token has flying and it isn't legendary.

Assault Strobe

Target creature gains double strike until end of turn. (It deals both first-strike and regular combat damage.)

Rockfall Vale

Rockfall Vale enters tapped unless you control two or more other lands.
{T}: Add {R} or {G}.

Dig Through Time

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
Look at the top seven cards of your library. Put two of them into your hand and the rest on the bottom of your library in any order.

Arcane Signet

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

Spark Double

You may have Spark Double enter as a copy of a creature or planeswalker you control, except it enters with an additional +1/+1 counter on it if it's a creature, it enters with an additional loyalty counter on it if it's a planeswalker, and it isn't legendary.

Command Tower

Ral, Leyline Prodigy

Ral, Leyline Prodigy enters with an additional loyalty counter on him for each instant and sorcery spell you've cast this turn.
+1: Until your next turn, instant and sorcery spells you cast cost {1} less to cast.
−2: Ral deals 2 damage divided as you choose among one or two targets. Draw a card if you control a blue permanent other than Ral.
−8: Exile the top eight cards of your library. You may cast instant and sorcery spells from among them this turn without paying their mana costs.

Ral, Monsoon Mage

Instant and sorcery spells you cast cost {1} less to cast.
Whenever you cast an instant or sorcery spell during your turn, flip a coin. If you lose the flip, Ral, Monsoon Mage deals 1 damage to you. If you win the flip, you may exile Ral. If you do, return him to the battlefield transformed under his owner's control.

Ral, Monsoon Mage // Ral, Leyline Prodigy

Sulfur Falls

Sulfur Falls enters tapped unless you control an Island or a Mountain.
{T}: Add {U} or {R}.

Access Tunnel

{T}: Add {C}.
{3}, {T}: Target creature with power 3 or less can't be blocked this turn.

Goblin Electromancer

Instant and sorcery spells you cast cost {1} less to cast.

Eureka Moment

Draw two cards. You may put a land card from your hand onto the battlefield.

Open the Way

X can't be greater than the number of players in the game.
Reveal cards from the top of your library until you reveal X land cards. Put those land cards onto the battlefield tapped and the rest on the bottom of your library in a random order.

Rootbound Crag

Rootbound Crag enters tapped unless you control a Mountain or a Forest.
{T}: Add {R} or {G}.

Unexpected Windfall

Case of the Ransacked Lab

Instant and sorcery spells you cast cost {1} less to cast.
To solve — You've cast four or more instant and sorcery spells this turn. (If unsolved, solve at the beginning of your end step.)
Solved — Whenever you cast an instant or sorcery spell, draw a card.

Explosive Singularity

As an additional cost to cast this spell, you may tap any number of untapped creatures you control. This spell costs {1} less to cast for each creature tapped this way.
Explosive Singularity deals 10 damage to any target.

Immolating Gyre

Immolating Gyre deals X damage to each creature and planeswalker you don't control, where X is the number of instant and sorcery cards in your graveyard.

Karplusan Forest

{T}: Add {C}.
{T}: Add {R} or {G}. Karplusan Forest deals 1 damage to you.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Magma Opus

Magma Opus deals 4 damage divided as you choose among any number of targets. Tap two target permanents. Create a 4/4 blue and red Elemental creature token. Draw two cards.
{U/R}{U/R}, Discard Magma Opus: Create a Treasure token.

Breeding Pool

({T}: Add {G} or {U}.)
As Breeding Pool enters, you may pay 2 life. If you don't, it enters tapped.

Ponder

Look at the top three cards of your library, then put them back in any order. You may shuffle.
Draw a card.

Reliquary Tower

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

Storm-Kiln Artist

Storm-Kiln Artist gets +1/+0 for each artifact you control.
Magecraft — Whenever you cast or copy an instant or sorcery spell, create a Treasure token.

Stomping Ground

({T}: Add {R} or {G}.)
As Stomping Ground enters, you may pay 2 life. If you don't, it enters tapped.

Archmage Emeritus

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