Time Sieve + Encroaching Mycosynth + Rionya, Fire Dancer + Abhorrent Overlord

Time Sieve

Encroaching Mycosynth

Rionya, Fire Dancer

Abhorrent Overlord

How it works

1. At the beginning of your combat phase, Rionya triggers, creating at least one token copy of Abhorrent Overlord with haste.
2. When the Abhorrent Overlord token enters the battlefield, it triggers, creating at least four 1/1 Harpy creature tokens.
3. Activate Time Sieve by tapping it, sacrificing the Abhorrent Overlord token and the Harpy tokens, causing you to take an extra turn after this one.
4. Repeat each turn.