Power from the ash.
The Obsidian Mind is a Warlock helmet specifically for use by a Voidwalker. When you use a Nova Bomb super against your enemies, the exotic perk, Insatiable, grants you an increased cooldown for your next Nova Bomb. How far your super bar is filled after a Nova Bomb is thrown depends on how many enemies are killed within the blast. In this regard, the Obsidian Mind is perfect for PVE where large groups of adds tend to congregate however in PVP it can be very limited due to the fact that it is often a rare occurrence that large groups of enemy guardians are in one area.
The Obsidian Mind has a very simple look but belies the mystery and power of the void and through that, the Voidwalker. The black colour tends to merge with every armour piece and the scuffs along the front and the sides, show a helmet that has been well used in the fight against the Darkness.
How to Acquire it?
The Obsidian Mind can be gained from an exotic helmet engram or purchasing it from Xur if you are lucky enough for him to have it in his inventory.