Mjolnir Powered Assault Armor/Helioskrill

The Helioskrill Armor is a new armor featured in Halo 5: Guardians. It is unlocked when you get the Legend Achievement in Halo: The Master Chief Collection. This Achievement is unlocked when the player completes all four campaigns on Legendary difficulty

Description
The HELIOSKRILL is a work of art crafted by a Sangheili prodigy inspired to test her skill against the best that humanity could muster.