Karn, the Great Creator + Ugin's Nexus + Throne of Geth + Flux Channeler

Karn, the Great Creator

Ugin's Nexus

Throne of Geth

Flux Channeler

How it works

1. Activate Throne of Geth by tapping it and sacrificing Ugin's Nexus.
2. Ugin's Nexus is exiled instead of being put into your graveyard, causing you to take an extra turn after this one.
3. Resolve the Throne of Geth ability, putting a loyalty counter on Karn.
4. Activate Karn's second loyalty ability by removing two loyalty counters from it, returning Ugin's Nexus from exile to your hand.
5. Move to your next turn.
6. Cast Ugin's Nexus by paying 5.
7. Flux Channeler triggers, putting a loyalty counter on Karn.
8. Repeat.

This intricate loop locks down your opponents and grants you infinite turns by endlessly recasting and sacrificing Ugin's Nexus. Because Throne of Geth lets you sacrifice the Nexus to proliferate, the Nexus's own replacement effect exiles it instead of letting it hit the graveyard, triggering its extra turn reward. From there, Karn, the Great Creator uses his minus ability to pluck Ugin's Nexus right back out of exile into your hand. Meanwhile, Flux Channeler ensures that casting the artifact over and over keeps generating extra counters to fuel Karn's loyalty.