Activate Rex using Steelswarm Operator's second ability by tapping it, adding {U}{U} that can only be spent to activate abilities of artifact sources.
Activate Rex using Knacksaw Clique's ability by paying {1}{U} and untapping it, exiling the top card of an opponent's library with the ability to play that card this turn.
Repeat.

Exile each opponent's library

Rex, Cyber-Hound

Knacksaw Clique

Steelswarm Operator

Activate Steelswarm Operator's second ability by tapping it, adding {U}{U} that can only be spent to activate abilities of artifacts.
Activate Freed from the Real by paying {U}, untapping Steelswarm Operator.
Repeat.

Infinite blue mana that can only be spent to activate abilities of artifacts

Infinite blue mana that can only be spent to cast artifact spells

Encroaching Mycosynth

Freed from the Real

Activate Steelswarm Operator's second ability by tapping it, adding {U}{U} that can only be spent to activate abilities of artifacts.
Activate Filigree Sages by paying {U}, untapping Steelswarm Operator.
Repeat.

Infinite mana artifacts you control can produce

Infinite untap of artifacts you control

Filigree Sages

Training Grounds

Activate Steelswarm Operator's second ability by tapping it, adding {U}{U} that can only be spent to activate abilities of artifacts.
Activate Steelswarm Operator using Horseshoe Crab's ability by paying {U}, untapping it.
Repeat.

Combos with "Steelswarm Operator"