Voidfang Vestments is the only Exotic Chest designed for Voidwalkers, and one of three Warlock chests total. Voidfang adds an extra seeker to your Axion Bolt and grants full grenade energy on spawn. If you're a Sunsinger with the Gift of the Sun talent (+1 Grenade), it will spawn you with 2 grenades.
If you're a long-time Warlock, it's highly unlikely you don't already own this; Xûr sold it 7 times in a 10-week span. It's one of two Exotics tailored to Voidwalkers, with Skull of Dire Ahamkara being the other.