Consider

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

Overpowering Attack

Freerunning {2}{R} (You may cast this spell for its freerunning cost if you dealt combat damage to a player this turn with an Assassin or commander.)
Untap all creatures you control that attacked this turn. If it's your main phase, there is an additional combat phase after this phase, followed by an additional main phase.

Jeska's Will

Choose one. If you control a commander as you cast this spell, you may choose both instead.
• Add {R} for each card in target opponent's hand.
• Exile the top three cards of your library. You may play them this turn.

Command Tower

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

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.

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control. It can attack and {T} no matter when it came under your control.)
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Niv-Mizzet, Parun

This spell can't be countered.
Flying
Whenever you draw a card, Niv-Mizzet deals 1 damage to any target.
Whenever a player casts an instant or sorcery spell, you draw a card.

Hullbreaker Horror

Flash
This spell can't be countered.
Whenever you cast a spell, choose up to one —
• Return target spell you don't control to its owner's hand.
• Return target nonland permanent to its owner's hand.

Young Pyromancer

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

Tidechannel Pathway

Barkchannel Pathway

Barkchannel Pathway // Tidechannel Pathway

Wooded Foothills

{T}, Pay 1 life, Sacrifice this land: Search your library for a Mountain or Forest card, put it onto the battlefield, then shuffle.

Stormcarved Coast

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

Expedite

Target creature gains haste until end of turn.
Draw a card.

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.

Frontier Bivouac

This land enters tapped.
{T}: Add {G}, {U}, or {R}.

Flooded Grove

{T}: Add {C}.
{G/U}, {T}: Add {G}{G}, {G}{U}, or {U}{U}.

Snap

Return target creature to its owner's hand. Untap up to two lands.

Hedge Maze

({T}: Add {G} or {U}.)
This land enters tapped.
When this land enters, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Sword of Feast and Famine

Equipped creature gets +2/+2 and has protection from black and from green.
Whenever equipped creature deals combat damage to a player, that player discards a card and you untap all lands you control.
Equip {2}

Preordain

Scry 2, then draw a card. (To scry 2, look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Veyran, Voice of Duality

Magecraft — Whenever you cast or copy an instant or sorcery spell, Veyran gets +1/+1 until end of turn.
If you casting or copying an instant or sorcery spell causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Scalding Tarn

{T}, Pay 1 life, Sacrifice this land: Search your library for an Island or Mountain card, put it onto the battlefield, then shuffle.

Cascade Bluffs

{T}: Add {C}.
{U/R}, {T}: Add {U}{U}, {U}{R}, or {R}{R}.

Elemental Eruption

Create a 4/4 red Dragon Elemental creature token with flying and prowess.
Storm (When you cast this spell, copy it for each spell cast before it this turn.)

Ponder

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

Ketria Triome

({T}: Add {G}, {U}, or {R}.)
This land 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.)

Arcane Signet

Regrowth

Return target card from your graveyard to your hand.

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.)

Insist

The next creature spell you cast this turn can't be countered.
Draw a card.

Seething Song

Boltwave

Boltwave deals 3 damage to each opponent.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

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.

Counterspell

Rockfall Vale

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

Exotic Orchard

{T}: Add one mana of any color that a land an opponent controls could produce.

Gitaxian Probe

({U/P} can be paid with either {U} or 2 life.)
Look at target player's hand.
Draw a card.

Ashling, Flame Dancer

You don't lose unspent red mana as steps and phases end.
Magecraft — Whenever you cast or copy an instant or sorcery spell, discard a card, then draw a card. If this is the second time this ability has resolved this turn, Ashling deals 2 damage to each opponent and each creature they control. If it's the third time, add {R}{R}{R}{R}.

Chandra's Ignition

Target creature you control deals damage equal to its power to each other creature and each opponent.

Manamorphose

Add two mana in any combination of colors.
Draw a card.

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 token: Add one mana of any color.")

Reliquary Tower

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

Spire Garden

This land enters tapped unless you have two or more opponents.
{T}: Add {R} or {G}.

Abundant Growth

Enchant land
When this Aura enters, draw a card.
Enchanted land has "{T}: Add one mana of any color."

Brainstorm

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

Charge Through

Target creature gains trample until end of turn.
Draw a card.

Lizard Blades

Double strike
Equipped creature has double strike.
Reconfigure {2} ({2}: Attach to target creature you control; or unattach from a creature. Reconfigure only as a sorcery. While attached, this isn't a creature.)

Mana Geyser

Add {R} for each tapped land your opponents control.

Breeding Pool

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

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Enter the Enigma

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

Training Center

This land enters tapped unless you have two or more opponents.
{T}: Add {U} or {R}.

Rogue's Passage

{T}: Add {C}.
{4}, {T}: Target creature can't be blocked this turn.

Fire-Lit Thicket

{T}: Add {C}.
{R/G}, {T}: Add {R}{R}, {R}{G}, or {G}{G}.

Overmaster

The next instant or sorcery spell you cast this turn can't be countered.
Draw a card.

Hinterland Harbor

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

Farseek

Search your library for a Plains, Island, Swamp, or Mountain card, put it onto the battlefield tapped, then shuffle.

Ice Storm

Ragavan, Nimble Pilferer

Whenever Ragavan deals combat damage to a player, create a Treasure token and exile the top card of that player's library. Until end of turn, you may cast that card.
Dash {1}{R} (You may cast this spell for its dash cost. If you do, it gains haste, and it's returned from the battlefield to its owner's hand at the beginning of the next end step.)

Storm-Kiln Artist

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

Temple of Cyclical Time

(Transforms from Ojer Pakpatiq, Deepest Epoch.)
{T}: Add {U}. Remove a time counter from this land.
{2}{U}, {T}: Transform this land. Activate only if it has no time counters on it and only as a sorcery.

Ojer Pakpatiq, Deepest Epoch

Flying
Whenever you cast an instant spell from your hand, it gains rebound. (Exile it as it resolves. At the beginning of your next upkeep, you may cast it from exile without paying its mana cost.)
When Ojer Pakpatiq dies, return it to the battlefield tapped and transformed under its owner's control with three time counters on it.

Ojer Pakpatiq, Deepest Epoch // Temple of Cyclical Time

Explore

You may play an additional land this turn.
Draw a card.

Wild Cantor

({R/G} can be paid with either {R} or {G}.)
Sacrifice this creature: Add one mana of any color.

Goblin Anarchomancer

Each spell you cast that's red or green costs {1} less to cast.

Goblin Electromancer

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

Dreamroot Cascade

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

Mox Amber

{T}: Add one mana of any color among legendary creatures and planeswalkers you control.

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 greater.

Misty Rainforest

{T}, Pay 1 life, Sacrifice this land: Search your library for a Forest or Island card, put it onto the battlefield, then shuffle.

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.

Archmage Emeritus

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

Lavaglide Pathway

Riverglide Pathway

Riverglide Pathway // Lavaglide Pathway

The Great Work

(As this Saga enters and after your draw step, add a lore counter.)
I — This Saga deals 3 damage to target opponent and each creature they control.
II — Create three Treasure tokens.
III — Until end of turn, you may cast instant and sorcery spells from any graveyard. If a spell cast this way would be put into a graveyard, exile it instead. Exile this Saga, then return it to the battlefield (front face up).

Urabrask

First strike
Whenever you cast an instant or sorcery spell, Urabrask deals 1 damage to target opponent. Add {R}.
{R}: Exile Urabrask, then return it to the battlefield transformed under its owner's control. Activate only as a sorcery and only if you've cast three or more instant and/or sorcery spells this turn.

Urabrask // The Great Work

Bria, Riptide Rogue

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Other creatures you control have prowess. (If a creature has multiple instances of prowess, each triggers separately.)
Whenever you cast a noncreature spell, target creature you control can't be blocked this turn.

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

Third Path Iconoclast

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

Steam Vents

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

Rootbound Crag

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

Forest

Island

Thundering Falls

({T}: Add {U} or {R}.)
This land enters tapped.
When this land enters, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Growth Spiral

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

Commercial District

({T}: Add {R} or {G}.)
This land enters tapped.
When this land enters, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Sulfur Falls

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

Timbercrown Pathway

Cragcrown Pathway

Cragcrown Pathway // Timbercrown Pathway

Sol Ring

Serum Visions

Mountain

Frantic Search

Draw two cards, then discard two cards. Untap up to three lands.

Time Warp

Target player takes an extra turn after this one.

Rejuvenating Springs

This land enters tapped unless you have two or more opponents.
{T}: Add {G} or {U}.

Crackle with Power

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

Stomping Ground

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