Time Sieve + Mycosynth Lattice + Rionya, Fire Dancer + Lena, Selfless Champion

Time Sieve

Mycosynth Lattice

Rionya, Fire Dancer

Lena, Selfless Champion

How it works

1. At the beginning of your combat phase, Rionya triggers, creating at least one token copy of Lena with haste.
2. Put the Lena token into your graveyard due to the legend rule.
3. The Lena token enters-the-battlefield ability triggers, creating at least five 1/1 Soldier creature tokens.
4. Activate Time Sieve by tapping it, sacrificing the Lena token and the Soldier tokens, causing you to take an extra turn after this one.
5. Repeat each turn.