Saving Grace enters the battlefield attached to Crystalline Crawler, triggering itself, causing all damage that would be dealt to you or permanents you control this turn to be dealt to Crystalline Crawler instead.
Activate Pestilence by paying ({B} magic symbol) , dealing 1 damage to each creature and each player.
Saving Grace's ability redirects damage to Crystalline Crawler, which results in at least three +1/+1 counters being placed on it instead due to Vigor.
Activate Crystalline Crawler's first activated ability at least once by removing at least one +1/+1 counter from it, adding at least ({B} magic symbol) .
Repeat from step 3.
Results
Infinite +1/+1 counters on Crystalline Crawler.
Infinite colored mana.
Infinite damage to opponent and each creature your opponents control.
Near-infinite +1/+1 counters on all other creatures you control.