Mechanized Production + Ugin's Nexus + Isochron Scepter + Reality Ripple

Mechanized Production

Ugin's Nexus

Isochron Scepter

Reality Ripple

How it works

1. At the beginning of your upkeep, Mechanized Production triggers, creating a token copy of Ugin's Nexus.
2. Put the token copy of Ugin's Nexus into exile due to the legend rule, causing you to take an extra turn after this one.
3. Activate Isochron Scepter by paying 2 and tapping it, casting a copy of Reality Ripple without paying its mana cost.
4. Resolve Reality Ripple, causing Ugin's Nexus and Mechanized Production to phase out.
5. Move to your next turn.
6. At the beginning of your untap step, Mechanized Production and Ugin's Nexus phase in.
7. Repeat.