Rootha, Mercurial Artist | Turnabout | Alchemist's Refuge

Cards

All other lands you control can tap to produce at least ({4} magic symbol) ({U} magic symbol) ({R} magic symbol) .

Activate all mana-producing lands you control except
Alchemist's Refuge by tapping them, adding at least ({4} magic symbol) ({U} magic symbol) ({R} magic symbol) .
Activate
Alchemist's Refuge's second ability by paying ({G} magic symbol) ({U} magic symbol) and tapping it, allowing you to cast spells this turn as though they had flash.
Cast
Turnabout by paying ({2} magic symbol) ({U} magic symbol) ({U} magic symbol) .
Holding priority, activate
Rootha by paying ({2} magic symbol) and returning it from the battlefield to your hand, copying
Turnabout.
Resolve the copy of
Turnabout, untapping all lands you control.
Activate all mana-producing lands you control by tapping them, adding at least ({4} magic symbol) ({U} magic symbol) ({R} magic symbol) .
Cast
Rootha by paying ({1} magic symbol) ({U} magic symbol) ({R} magic symbol) .
Repeat from step 4.