Carth the Lion + Karn, the Great Creator + Ugin's Nexus + Oath of Teferi + Krark-Clan Ironworks

Carth the Lion

Karn, the Great Creator

Ugin's Nexus

Oath of Teferi

Krark-Clan Ironworks

How it works

1. Activate Krark-Clan Ironworks by exiling Ugin's Nexus, adding CC.
2. Ugin's Nexus triggers, causing you to take an extra turn after this one.
3. Activate Karn's first loyalty ability by putting two loyalty counters on it, causing any artifact to become an artifact creature until end of turn.
4. Activate Karn's second loyalty ability by removing a loyalty counter 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. Repeat.