Cast Walk the Aeons by paying {4}{U}{U}, causing you to take an extra turn after this one.
Move to your next turn.
Activate Kylox's Voltstrider's first ability by exiling Walk the Aeons from your graveyard, causing Kylox's Voltstrider to become an artifact creature until end of turn.
Declare Kylov's Voltstrider as an attacker.
Kylox's Voltstrider triggers, causing you to pay {4}{U}{U} to cast Walk the Aeons from exile.
Resolve Walk the Aeons, causing you to take an extra turn after this one, and put Walk the Aeons on the bottom of your library.
Move to your next turn, drawing Walk the Aeons from the bottom of your library due to River Song.
Repeat.

Infinite turns

River Song

Kylox's Voltstrider

Walk the Aeons

Cast Time Stretch by paying {8}{U}{U}, causing you to take two extra turns after this one.
Move to your second extra turn.
Activate Kylox's Voltstrider's first ability by exiling Time Stretch from your graveyard, causing Kylox's Voltstrider to become an artifact creature until end of turn.
Declare Kylov's Voltstrider as an attacker.
Kylox's Voltstrider triggers, causing you to pay {8}{U}{U} to cast Time Stretch from exile.
Resolve Time Stretch, causing you to take two extra turns after this one, and put Time Stretch on the bottom of your library.
Move to your first extra turn, drawing Time Stretch from the bottom of your library due to River Song.
Move to your second extra turn.
Repeat.

Combos with "Kylox's Voltstrider"