At the beginning of your upkeep, Mechanized Production triggers, creating a token copy of Ugin's Nexus.
The token copy of Ugin's Nexus is put into exile as a state based action due to the legend rule, causing you to take an extra turn after this one.
Move to your next turn.
Repeat.

Infinite turns

Lock

Ugin's Nexus

Tamiyo's Compleation

Mechanized Production

At the beginning of your end step, Artificer Class triggers, creating a token copy of Ugin's Nexus.
Put the token Ugin's Nexus into exile due to the legend rule, causing you to take an extra turn after this one.
Repeat each turn.

Artificer Class

At the beginning of your upkeep, Extravagant Replication triggers, creating a token copy of Ugin's Nexus.
Put the token Ugin's Nexus into exile due to the legend rule, causing you to take an extra turn after this one.
Repeat each turn.

Extravagant Replication

Activate Cogwork Assembler by paying {7}, creating a token copy of Ugin's Nexus.
The token copy of Ugin's Nexus is put into exile as a state based action due to the legend rule, causing you to take an extra turn after this one.
Move to your next turn.
Repeat.

Combos with "Tamiyo's Compleation"