Kadru the Death Serpent

Kadru is the goddess of the yuan-ti. She is described as a fiendish colossal black-and-yellow snake with exaggerated fractal-like parts: a tongue that forks infinitely, hundreds of rows of fangs, scales that protrude backward like sharp horns, and stripes made of smaller stripes made of smaller stripes.
A typical shrine to Kadru contains an upward-pointed spear with a yellow-and-black painted serpent coiling around it. A bowl for sacrificial bloodletting is placed where the spear protrudes from the ground.
The yuan-ti spawned on Feather Island during Origination. Around year 90, Kadru appeared to them and proclaimed herself their goddess. Some yuan-ti happily obliged this powerful serpentine overlord, sacrificing victims to her in exchange for more power. Her followers then used this power to take seize control of their society. Later, when mainland society docked on Feather Island in the year 191, the united yuan-ti empire turned their sights westward.