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.