Timestream Navigator on the battlefield (without summoning sickness).
Easy Prerequisites
You control nine or more permanents and/or have the city's blessing.
Mana Needed
({4} magic symbol) ({U} magic symbol) ({U} magic symbol) the first turn, plus ({2} magic symbol) ({U} magic symbol) ({U} magic symbol) each turn available.
Steps
Cast
Echocasting Symposium by paying ({4} magic symbol) ({U} magic symbol) ({U} magic symbol) , creating a token copy of
Timestream Navigator and exiling
Echocasting Symposium.
If you don't have the city's blessing, the
Timestream Navigators will give you the city's blessing.
Activate the oldest
Timestream Navigator by paying ({2} magic symbol) ({U} magic symbol) ({U} magic symbol) , tapping it and putting it from the battlefield onto the bottom of your library, causing you to take an extra turn after this one.
Move to your next turn. At the beginning of your precombat main phase,
Echocasting Symposium's paradigm ability triggers, causing you to cast a copy of it from exile. Resolve the copy, creating a token copy of
Timestream Navigator.
Repeat from step 3.
Results
Infinite turns.
Metadata
This combo produces a lock.
Bracket Tag
This combo has been estimated to be Ruthless (Bracket 4+).