Arc Infinite Edge

Arc Infinite Edge is a Legendary Sword that can be obtained through the quest A Tale of Two Guardians.

Exploits
The guard function for this sword provides substantial damage resistance, capable of keeping a Guardian alive when Crota uses his Oversoul in the Crota's End Raid, and Skolas's Devouring Essense in the Prison of Elders challenge Skolas's Revenge, provided they are actively blocking.