Snake Pit

Whenever an opponent casts a blue or black spell, you may create a 1/1 green Snake creature token.

Ardbert, Warrior of Darkness

Whenever you cast a white spell, put a +1/+1 counter on each legendary creature you control. They gain vigilance until end of turn.
Whenever you cast a black spell, put a +1/+1 counter on each legendary creature you control. They gain menace until end of turn.

Threefold Signal

When this artifact enters, scry 3.
Each spell you cast that's exactly three colors has replicate {3}. (When you cast it, copy it for each time you paid its replicate cost. You may choose new targets for the copies. A copy of a permanent spell becomes a token.)

Thornscape Familiar

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

Aragorn, the Uniter

Whenever you cast a white spell, create a 1/1 white Human Soldier creature token.
Whenever you cast a blue spell, scry 2.
Whenever you cast a red spell, Aragorn deals 3 damage to target opponent.
Whenever you cast a green spell, target creature gets +4/+4 until end of turn.

Insight

Whenever an opponent casts a green spell, you draw a card.

Lightning Cloud

Whenever a player casts a red spell, you may pay {R}. If you do, this enchantment deals 1 damage to any target.

Fallaji Wayfarer

Fallaji Wayfarer is all colors. This ability doesn't affect its color identity. (It can be in any deck whose commander's color identity includes green.)
Multicolored spells you cast have convoke. (Your creatures can help cast those spells. Each creature you tap while casting a multicolored spell pays for {1} or one mana of a color that creature is.)

Sol'kanar the Swamp King

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
Whenever a player casts a black spell, you gain 1 life.

The Darkness Crystal

Black spells you cast cost {1} less to cast.
If a nontoken creature an opponent controls would die, instead exile it and you gain 2 life.
{4}{B}{B}, {T}: Put target creature card exiled with The Darkness Crystal onto the battlefield tapped under your control with two additional +1/+1 counters on it.

Fable of Wolf and Owl

Whenever you cast a green spell, you may create a 2/2 green Wolf creature token.
Whenever you cast a blue spell, you may create a 1/1 blue Bird creature token with flying.

Merrow Bonegnawer

{T}: Target player exiles a card from their graveyard.
Whenever you cast a black spell, you may untap this creature.

Circu, Dimir Lobotomist

Whenever you cast a blue spell, exile the top card of target player's library.
Whenever you cast a black spell, exile the top card of target player's library.
Your opponents can't cast spells with the same name as a card exiled with Circu.

Drowned Secrets

Whenever you cast a blue spell, target player mills two cards.

God-Pharaoh's Faithful

Whenever you cast a blue, black, or red spell, you gain 1 life.

Tibor and Lumia

Whenever you cast a blue spell, target creature gains flying until end of turn.
Whenever you cast a red spell, Tibor and Lumia deals 1 damage to each creature without flying.

Goblin Battle Jester

Whenever you cast a red spell, target creature can't block this turn.

Nightscape Familiar

Blue spells and red spells you cast cost {1} less to cast.
{1}{B}: Regenerate this creature.

Demon's Horn

Whenever a player casts a black spell, you may gain 1 life.

K'rrik, Son of Yawgmoth

({B/P} can be paid with either {B} or 2 life.)
Lifelink
For each {B} in a cost, you may pay 2 life rather than pay that mana.
Whenever you cast a black spell, put a +1/+1 counter on K'rrik.

Shrine of Piercing Vision

At the beginning of your upkeep and whenever you cast a blue spell, put a charge counter on this artifact.
{T}, Sacrifice this artifact: Look at the top X cards of your library, where X is the number of charge counters on this artifact. Put one of those cards into your hand and the rest on the bottom of your library in any order.

Jenson Carthalion, Druid Exile

Whenever you cast a multicolored spell, scry 1. If that spell was all colors, create a 4/4 white Angel creature token with flying and vigilance.
{5}, {T}: Add {W}{U}{B}{R}{G}.

Rewards of Diversity

Whenever an opponent casts a multicolored spell, you gain 4 life.

Jodah, the Unifier

Legendary creatures you control get +X/+X, where X is the number of legendary creatures you control.
Whenever you cast a legendary spell from your hand, exile cards from the top of your library until you exile a legendary nonland card with lesser mana value. You may cast that card without paying its mana cost. Put the rest on the bottom of your library in a random order.

Thunderscape Familiar

First strike
Black spells and green spells you cast cost {1} less to cast.

Staff of the Mind Magus

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

Intimidator Initiate

Whenever a player casts a red spell, you may pay {1}. If you do, target creature can't block this turn.

The Water Crystal

Blue spells you cast cost {1} less to cast.
If an opponent would mill one or more cards, they mill that many cards plus four instead.
{4}{U}{U}, {T}: Each opponent mills cards equal to the number of cards in your hand.

Spellbane Centaur

Creatures you control can't be the targets of blue spells or abilities from blue sources.

Grand Arbiter Augustin IV

White spells you cast cost {1} less to cast.
Blue spells you cast cost {1} less to cast.
Spells your opponents cast cost {1} more to cast.

Widespread Thieving

Hideaway 5 (When this enchantment enters, look at the top five cards of your library, exile one face down, then put the rest on the bottom in a random order.)
Whenever you cast a multicolored spell, create a Treasure token. Then you may pay {W}{U}{B}{R}{G}. If you do, you may play the exiled card without paying its mana cost.

Pyroconvergence

Whenever you cast a multicolored spell, this enchantment deals 2 damage to any target.

Hero of Precinct One

Whenever you cast a multicolored spell, create a 1/1 white Human creature token.

Urza's Filter

Multicolored spells cost {2} less to cast.

General Ferrous Rokiric

Hexproof from monocolored
Whenever you cast a multicolored spell, create a 4/4 red and white Golem artifact creature token.

Soot Imp

Flying
Whenever a player casts a nonblack spell, that player loses 1 life.

Balefire Liege

Other red creatures you control get +1/+1.
Other white creatures you control get +1/+1.
Whenever you cast a red spell, this creature deals 3 damage to target player or planeswalker.
Whenever you cast a white spell, you gain 3 life.

The Fire Crystal

Red spells you cast cost {1} less to cast.
Creatures you control have haste.
{4}{R}{R}, {T}: Create a token that's a copy of target creature you control. Sacrifice it at the beginning of the next end step.

Shrine of Boundless Growth

At the beginning of your upkeep and whenever you cast a green spell, put a charge counter on this artifact.
{T}, Sacrifice this artifact: Add {C} for each charge counter on this artifact.

Meeting of the Five

Exile the top ten cards of your library. You may cast spells with exactly three colors from among them this turn. Add {W}{W}{U}{U}{B}{B}{R}{R}{G}{G}. Spend this mana only to cast spells with exactly three colors.

Stormscape Familiar

Flying
White spells and black spells you cast cost {1} less to cast.

Sunscape Familiar

Defender (This creature can't attack.)
Green spells and blue spells you cast cost {1} less to cast.

Staff of the Death Magus

Whenever you cast a black spell or a Swamp you control enters, you gain 1 life.

Kraken's Eye

Whenever a player casts a blue spell, you may gain 1 life.

Thrun, Breaker of Silence

This spell can't be countered.
Trample
Thrun can't be the target of nongreen spells your opponents control or abilities from nongreen sources your opponents control.
During your turn, Thrun has indestructible.

Deathbringer Liege

Other white creatures you control get +1/+1.
Other black creatures you control get +1/+1.
Whenever you cast a white spell, you may tap target creature.
Whenever you cast a black spell, you may destroy target creature if it's tapped.

Ricochet Trap

If an opponent cast a blue spell this turn, you may pay {R} rather than pay this spell's mana cost.
Change the target of target spell with a single target.

Mana Cannons

Whenever you cast a multicolored spell, this enchantment deals X damage to any target, where X is the number of colors that spell is.