There and Back Again and Orvar on the battlefield.
There and Back Again has exactly two lore counters on it.
({3} magic symbol) ({W} magic symbol) available.
Steps
At the beginning of your precombat main phase, There and Back Again triggers, creating a legendary 6/6 Smaug creature token, and causing you to sacrifice There and Back Again.
Cast Change of Heart with buyback by paying ({3} magic symbol) ({W} magic symbol) , targeting the Smaug token.
Orvar's first ability triggers, creating a copy of the Smaug token.
Put the new Smaug token into your graveyard due to the legend rule.
When Smaug dies, it triggers, creating fourteen Treasure tokens.
Resolve Change of Heart from step 2, returning it to your hand.
Activate four Treasures by tapping and sacrificing them, adding ({3} magic symbol) ({W} magic symbol) .
Repeat from step 2.
Once you have infinite colored mana, you may instead target any other creature(s) you control using Change of Heart, to create infinite tokens of them using Orvar.