Untapping Creatures

Kindlespark Duo

{T}: This creature deals 1 damage to target opponent.
Whenever you cast a noncreature spell, untap this creature.

Unruly Catapult

Defender
{T}: This creature deals 1 damage to each opponent.
Whenever you cast an instant or sorcery spell, untap this creature.

Tapping Enchantments

Prophetic Ravings

Enchant creature
Enchanted creature has haste and "{T}, Discard a card: Draw a card."

Multani's Harmony

Enchant creature
Enchanted creature has "{T}: Add one mana of any color."

Fodder Generator

Murmuring Mystic

Whenever you cast an instant or sorcery spell, create a 1/1 blue Bird Illusion creature token with flying.

Tolarian Kraken

Whenever you draw a card, you may pay {1}. When you do, you may tap or untap target creature.

Stinging Lionfish

Whenever you cast your first spell during each opponent's turn, you may tap or untap target nonland permanent.

Copying

Swarm Intelligence

Whenever you cast an instant or sorcery spell, you may copy that spell. You may choose new targets for the copy.

Elmar, Ulvenwald Informant

Haste
Whenever you cast your second spell each turn, untap target creature, then investigate. (Create a colorless Clue artifact token with "{2}, Sacrifice this artifact: Draw a card.")
Friends forever (You can have two commanders if both have friends forever.)

Acceleration

Nature's Lore

Search your library for a Forest card, put that card onto the battlefield, then shuffle.

Haldan, Avid Arcanist

Partner with Pako, Arcane Retriever (When this creature enters, target player may put Pako into their hand from their library, then shuffle.)
You may play lands and cast noncreature spells from among cards you exiled that have fetch counters on them, and you may spend mana as though it were mana of any color to cast those spells.

Chakram Retriever

Partner with Chakram Slinger (When this creature enters, target player may put Chakram Slinger into their hand from their library, then shuffle.)
Whenever you cast a spell during your turn, untap target creature.

Explore

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

Arcane Bombardment

Whenever you cast your first instant or sorcery spell each turn, exile an instant or sorcery card at random from your graveyard. Then copy each card exiled with this enchantment. You may cast any number of the copies without paying their mana costs.

White Cards

Leonin Battlemage

{T}: Target creature gets +1/+1 until end of turn.
Whenever you cast a spell, you may untap this creature.

Hard Cover

Enchant creature
Enchanted creature gets +0/+2 and has "{T}: Draw a card, then discard a card."

Talrand, Sky Summoner

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

Questionable

Elemental Mastery

Enchant creature
Enchanted creature has "{T}: Create X 1/1 red Elemental creature tokens with haste, where X is this creature's power. Exile them at the beginning of the next end step."

Young Pyromancer

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

Primal Growth

Kicker—Sacrifice a creature. (You may sacrifice a creature in addition to any other costs as you cast this spell.)
Search your library for a basic land card, put that card onto the battlefield, then shuffle. If this spell was kicked, instead search your library for up to two basic land cards, put them onto the battlefield, then shuffle.

Blistercoil Weird

Whenever you cast an instant or sorcery spell, this creature gets +1/+1 until end of turn. Untap it.

Cinder Pyromancer

{T}: This creature deals 1 damage to target player or planeswalker.
Whenever you cast a red spell, you may untap this creature.

Sorcerer Class

(Gain the next level as a sorcery to add its ability.)
When this Class enters, draw two cards, then discard two cards.
{U}{R}: Level 2
Creatures you control have "{T}: Add {U} or {R}. Spend this mana only to cast an instant or sorcery spell or to gain a Class level."
{3}{U}{R}: Level 3
Whenever you cast an instant or sorcery spell, that spell deals damage to each opponent equal to the number of instant and sorcery spells you've cast this turn.

Aria of Flame

When this enchantment enters, each opponent gains 10 life.
Whenever you cast an instant or sorcery spell, put a verse counter on this enchantment, then it deals damage equal to the number of verse counters on it to target player or planeswalker.

Pink Horror

Coruscating Flames — Whenever you cast an instant or sorcery spell, this creature deals 2 damage to any target.
Split — When this creature dies, create two 2/2 blue and red Demon Horror creature tokens named Blue Horror with "Whenever you cast an instant or sorcery spell, this token deals 1 damage to any target."

Metallurgic Summonings

Whenever you cast an instant or sorcery spell, create an X/X colorless Construct artifact creature token, where X is that spell's mana value.
{3}{U}{U}, Exile this enchantment: Return all instant and sorcery cards from your graveyard to your hand. Activate only if you control six or more artifacts.

Gelectrode

{T}: This creature deals 1 damage to any target.
Whenever you cast an instant or sorcery spell, you may untap this creature.

Chandra, Roaring Flame

+1: Chandra deals 2 damage to target player or planeswalker.
−2: Chandra deals 2 damage to target creature.
−7: Chandra deals 6 damage to each opponent. Each player dealt damage this way gets an emblem with "At the beginning of your upkeep, this emblem deals 3 damage to you."

Chandra, Fire of Kaladesh

Whenever you cast a red spell, untap Chandra.
{T}: Chandra deals 1 damage to target player or planeswalker. If Chandra has dealt 3 or more damage this turn, exile her, then return her to the battlefield transformed under her owner's control.

Chandra, Fire of Kaladesh // Chandra, Roaring Flame

Roiling Regrowth

Sacrifice a land. Search your library for up to two basic land cards, put them onto the battlefield tapped, then shuffle.

Velocity

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.

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.

Pako, Arcane Retriever

Partner with Haldan, Avid Arcanist
Haste
Whenever Pako attacks, exile the top card of each player's library and put a fetch counter on each of them. Put a +1/+1 counter on Pako for each noncreature card exiled this way.

Cryptic Pursuit

Whenever you cast an instant or sorcery spell from your hand, manifest the top card of your library. (Put that card onto the battlefield face down as a 2/2 creature. Turn it face up any time for its mana cost if it's a creature card.)
Whenever a face-down creature you control dies, exile it if it's an instant or sorcery card. You may cast that card until the end of your next turn.

Harrow

As an additional cost to cast this spell, sacrifice a land.
Search your library for up to two basic land cards, put them onto the battlefield, then shuffle.

Thermo-Alchemist

Farseek

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

Fiery Inscription

When this enchantment enters, the Ring tempts you.
Whenever you cast an instant or sorcery spell, this enchantment deals 2 damage to each opponent.

Mercurial Spelldancer

This creature can't be blocked.
Whenever you cast a noncreature spell, put an oil counter on this creature.
Whenever this creature deals combat damage to a player, you may remove two oil counters from it. If you do, when you next cast an instant or sorcery spell this turn, copy that spell. You may choose new targets for the copy.

Growth Spiral

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

Broken Bond

Destroy target artifact or enchantment. You may put a land card from your hand onto the battlefield.

Sphinx-Bone Wand

Whenever you cast an instant or sorcery spell, you may put a charge counter on this artifact. If you do, this artifact deals damage equal to the number of charge counters on it to any target.

Zephyr Scribe

{U}, {T}: Draw a card, then discard a card.
Whenever you cast a noncreature spell, untap this creature.

Ral, Storm Conduit

Whenever you cast or copy an instant or sorcery spell, Ral 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.

Dual Casting

Enchant creature
Enchanted creature has "{R}, {T}: Copy target instant or sorcery spell you control. You may choose new targets for the copy."

Sol Ring

Quicksilver Dagger

Enchant creature
Enchanted creature has "{T}: This creature deals 1 damage to target player or planeswalker. You draw a card."

Ocular Halo

Enchant creature
Enchanted creature has "{T}: Draw a card."
{W}: Enchanted creature gains vigilance until end of turn.

Merrow Levitator

{T}: Target creature gains flying until end of turn.
Whenever you cast a blue spell, you may untap this creature.

Summer Bloom

You may play up to three additional lands this turn.

Oracle's Insight

Enchant creature
Enchanted creature has "{T}: Scry 1, then draw a card." (To scry 1, look at the top card of your library, then you may put that card on the bottom.)

Blisterspit Gremlin

{1}, {T}: This creature deals 1 damage to each opponent.
Whenever you cast a noncreature spell, untap this creature.

Karametra's Favor

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

Pristine Skywise

Flying
Whenever you cast a noncreature spell, untap this creature. It gains protection from the color of your choice until end of turn.

Rampant Growth

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