The Sea-Serpent’s Coil is a Mythic Item in The Elder Scrolls Online found via the Antiquities system that grants increased damage resistance while at full Health, and Major Berserk and Major Courage after taking damage.
Sea-Serpent’s Coil Basic Information:
Bind: On Pickup
DLC: High Isle
(1 item) While at full Health, you gain 40% damage resistance. After taking damage while at full Health in combat, you gain Serpent’s Rebuke for 10 seconds, snaring yourself by 40% and gaining Major Berserk and Major Courage, increasing your damage done by 10% and Weapon and Spell Damage by 430.
The damage resistance does not apply while Serpent’s Rebuke is active.