Activate Yawgmoth's first ability by paying 1 life and sacrificing another creature, causing you to draw a card and allowing you to put a -1/-1 counter on up to one creature.
The Locust God and Sheoldred's first ability trigger.
Resolve the Locust God trigger, creating a 1/1 Insect creature token with flying and haste.
Resolve the Sheoldred trigger, causing you to gain 2 life.
Repeat.
This elegant loop is fueled by Yawgmoth, Thran Physician, whose active sacrifice engine lets you trade a creature and a life point to draw a card and place a -1/-1 counter. Each time you draw that card, The Locust God leaps into action to replace it with a fresh 1/1 flying Insect token, immediately supplying a fresh sacrifice fodder for Yawgmoth to consume again. Meanwhile, Sheoldred, the Apocalypse keeps your life total safely in the black by granting you 2 life for every single card drawn, turning what starts as a life-loss loop into a net-positive engine for infinite resources.