Time Sieve + Mycosynth Lattice + Rionya, Fire Dancer + Phylath, World Sculptor

Time Sieve

Mycosynth Lattice

Rionya, Fire Dancer

Phylath, World Sculptor

How it works

1. At the beginning of your combat phase, Rionya triggers, creating at least one token copy of Phylath with haste.
2. Put the Phylath token into your graveyard due to the legend rule.
3. The Phylath token enters-the-battlefield ability triggers, creating at least five 0/1 Plant creature tokens.
4. Activate Time Sieve by tapping it and sacrificing the Plant tokens, causing you to take an extra turn after this one.
5. Repeat each turn.