Ghired, Mirror of the Wilds | There and Back Again | High Alert

Cards

At the beginning of your precombat main phase,
There and Back Again triggers, putting a lore counter on it.
There and Back Again's third chapter ability triggers, creating a legendary 6/6 Smaug creature token and causing you to sacrifice
There and Back Again.
Activate
Ghired by tapping it, creating a copy of the Smaug token.
Put either Smaug token into your graveyard due to the legend rule.
When the Smaug token dies, it triggers, creating fourteen Treasure tokens.
Activate four Treasure tokens by tapping and sacrificing them, adding ({2} magic symbol) ({W} magic symbol) ({U} magic symbol) .
Activate
High Alert by paying ({2} magic symbol) ({W} magic symbol) ({U} magic symbol) , untapping
Ghired.
Repeat from step 3.

Once you have infinite mana, you may instead use
Ghired to copy any other token(s) that entered the battlefield under your control this turn.