Mendicant Core, Guidelight + Ugin's Nexus + Meticulous Excavation

Mendicant Core, Guidelight

Ugin's Nexus

Meticulous Excavation

How it works

1. Cast Ugin's Nexus by paying 5.
2. Mendicant Core triggers, copying the Ugin's Nexus spell.
3. Resolve both Ugin's Nexus spells.
4. The token Ugin's Nexus is put into exile due to the legend rule and its replacement effect, causing you to take an extra turn after this one.
5. Activate Meticulous Excavation by paying 2, returning Ugin's Nexus from the battlefield to your hand.
6. Repeat each turn.