General Ferrous Rokiric

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

Tome of the Guildpact

Whenever you cast a multicolored spell, draw a card.
{T}: Add one mana of any color.

Demand

Search your library for a multicolored card, reveal it, put it into your hand, then shuffle.

Supply

Create X 1/1 green Saproling creature tokens.

Supply // Demand

Obsidian Obelisk

This artifact enters tapped.
{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a multicolored spell.

Rienne, Angel of Rebirth

Flying
Other multicolored creatures you control get +1/+0.
Whenever another multicolored creature you control dies, return it to its owner's hand at the beginning of the next end step.

Maelstrom Wanderer

Creatures you control have haste.
Cascade, cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order. Then do it again.)

Maze Rusher

Haste
Multicolored creatures you control have haste.

Maze Behemoth

Trample
Multicolored creatures you control have trample.

Ink-Treader Nephilim

Whenever a player casts an instant or sorcery spell, if that spell targets only this creature, copy the spell for each other creature that spell could target. Each copy targets a different one of those creatures.

Pillar of the Paruns

{T}: Add one mana of any color. Spend this mana only to cast a multicolored spell.

Maze Sentinel

Vigilance
Multicolored creatures you control have vigilance.

Scuttling Butler

At the beginning of combat on your turn, if you control two or more multicolored permanents, this creature gains double strike until end of turn.

Reborn Hope

Return target multicolored card from your graveyard to your hand.

Maze Glider

Flying
Multicolored creatures you control have flying.

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.

Psychotic Fury

Target multicolored creature gains double strike until end of turn.
Draw a card.

Vivid Revival

Return up to three target multicolored cards from your graveyard to your hand. Exile Vivid Revival.

Kynaios and Tiro of Meletis

At the beginning of your end step, draw a card. Each player may put a land card from their hand onto the battlefield, then each opponent who didn't draws a card.

Rampaging Monument

Trample
This creature enters with three +1/+1 counters on it.
Whenever you cast a multicolored spell, put a +1/+1 counter on this creature.

Dragon Arch

{2}, {T}: You may put a multicolored creature card from your hand onto the battlefield.

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.

Omnath, Locus of Creation

When Omnath enters, draw a card.
Landfall — Whenever a land you control enters, you gain 4 life if this is the first time this ability has resolved this turn. If it's the second time, add {R}{G}{W}{U}. If it's the third time, Omnath deals 4 damage to each opponent and each planeswalker you don't control.

Urza's Filter

Multicolored spells cost {2} less to cast.

Brace for Impact

Prevent all damage that would be dealt to target multicolored creature this turn. For each 1 damage prevented this way, put a +1/+1 counter on that creature.

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.)

Hero of Precinct One

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