Jugan dies, triggering itself and Nim Deathmantle.
Resolve the Jugan trigger, putting five +1/+1 counters on Crystalline Crawler.
Activate Crystalline Crawler's first ability three times by removing three +1/+1 counters from it, adding ({3} magic symbol) .
Resolve the Nim Deathmantle trigger from step 2, causing you to pay ({4} magic symbol) to return Jugan from your graveyard to the battlefield, and attach Nim Deathmantle to it.
Resolve the Carrion Feeder ability from step 1, putting a +1/+1 counter on it.
Repeat.
Results
Infinite +1/+1 counters on all creatures you control except Jugan.