Glint-Horn Buccaneer triggers, dealing 1 damage to each opponent and causing you to gain that much life plus 1.
Cleric Class triggers, putting a +1/+1 counter on Benthic Biomancer.
Repeat from step 2.
This loop creates a self-sustaining cycle of counters, cards, and damage by turning a single +1/+1 counter on Benthic Biomancer into a flurry of triggers. Benthic Biomancer's triggered ability makes you draw and discard, which immediately commands Glint-Horn Buccaneer to deal damage to each opponent and grant you life. Thanks to Cleric Class's static ability boosting your lifegain and its Level 2 triggered ability rewarding you with a +1/+1 counter whenever you gain that life, Benthic Biomancer receives another counter to restart the entire sequence.