Riku of Two Reflections | Narset's Reversal | Karn's Temporal Sundering

Cards

Riku of Two Reflections on the battlefield.
Narset's Reversal and
Karn's Temporal Sundering in hand.
({4} magic symbol) ({U} magic symbol) ({U} magic symbol) ({U} magic symbol) ({U} magic symbol) ({U} magic symbol) ({R} magic symbol) each turn available.

Cast
Karn's Temporal Sundering by paying ({4} magic symbol) ({U} magic symbol) ({U} magic symbol) .
Riku's first ability triggers - choose not to pay.
Holding priority, cast
Narset's Reversal by paying ({U} magic symbol) ({U} magic symbol) , targeting
Karn's Temporal Sundering.
Riku's first ability triggers, causing you to pay ({U} magic symbol) ({R} magic symbol) to copy
Narset's Reversal, with the copy targeting the original
Narset's Reversal.
Resolve the copy of
Narset's Reversal, copying the original
Narset's Reversal targeting
Karn's Temporal Sundering, and returning the original
Narset's Reversal to your hand.
Resolve the copy of
Narset's Reversal created in step 5, copying
Karn's Temporal Sundering and returning the original
Karn's Temporal Sundering to your hand.
Resolve
Karn's Temporal Sundering, causing you to take an extra turn after this one.
Repeat each turn.

You may pay an additional ({U} magic symbol) ({R} magic symbol) to copy the extra turn spell, and only need to do this loop during your second extra turn.