Activate Timestream Navigator by paying {2}{U}{U}, tapping it and putting it on the bottom of your library from the battlefield, causing you to take an extra turn after this one.
Activate Fiend Artisan by paying {2}{B/G} and sacrificing Gravecrawler, causing you to search your library for Timestream Navigator and put it onto the battlefield.
Cast Gravecrawler from your graveyard by paying {B}.
Repeat each turn.

Infinite turns

Timestream Navigator

Gravecrawler

Fiend Artisan

Activate Timestream Navigator by paying {2}{U}{U}, tapping it and putting it on the bottom of your library from the battlefield, causing you to take an extra turn after this one.
Activate Fiend Artisan by paying {2}{B/G} and sacrificing Squee, causing you to search your library for Timestream Navigator and put it onto the battlefield.
Cast Squee from your graveyard by paying {1}{R}{R}.
Repeat each turn.

Combos with "Fiend Artisan"