Key Relics

Key Relics is a Relic from The Taken King Strikes and Story Missions

Console	Control
Action-based	Action (or Reload)
Default Playstation	Square
Default xBox	X

Up and down the strikes and stories from Taken King onward are relics that play a key-like role. Tomb husks stand out in my memory, but energy cores play a role in the Restorative Mind strike and the Fallen S.A.B.E.R. strike and Rise of Iron story missions. The all function similarly: pick up the key item relic with the action button and place it in its destination with the same button.

These cannot be thrown for damage, but are held as weak melee weapons. Think of a sword with no ammo! During your holding of them, your grenade recharge speeds up.

I don't know if this is a bug or not, but if you're trying to get ability kills for your swords or quests, key relic items used as melee weapons when your melee ability is charged counts as an ability kill and does not consume the charge. Each melee kill will count where the melee ability was charged will count as an ability kill without using the charge, so you can do it over and over.