Tome of the Guildpact

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

Simple

Pure

Pure // Simple

Hero of Precinct One

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

General Ferrous Rokiric

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

Ramos, Dragon Engine

Flying
Whenever you cast a spell, put a +1/+1 counter on Ramos for each of that spell's colors.
Remove five +1/+1 counters from Ramos: Add {W}{W}{U}{U}{B}{B}{R}{R}{G}{G}. Activate only once each turn.

Knight of New Alara

Each other multicolored creature you control gets +1/+1 for each of its colors.

Urza's Filter

Multicolored spells cost {2} less to cast.

Reborn Hope

Return target multicolored card from your graveyard to your hand.

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.

Demand

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