Activate Benthic Biomancer by paying 1, putting a +1/+1 counter on it.
Benthic Biomancer triggers, causing you to loot.
Starving Revenant triggers, causing you to gain 1 life and target opponent to lose 1 life.
Archangel of Thune triggers, putting a +1/+1 counter on each creature you control.
Repeat from step 2.
This clever loop is ignited by activating Benthic Biomancer's adapt ability to place a +1/+1 counter on itself, which immediately triggers its own looting ability to draw and discard a card. That draw triggers Starving Revenant's descend 8 ability (assuming you have at least eight permanent cards in your graveyard), causing an opponent to lose life and granting you life. In turn, Archangel of Thune sees this lifegain and places a +1/+1 counter on each creature you control, resetting Benthic Biomancer so you can pay to adapt it all over again.