From Destinypedia, the Destiny wiki
The Resonant Shard is encountered in the third encounter of the Vow of the Disciple Raid, Exibition. It functions similarly to a Vex Cranium. While holding it, the player's visual is switched to third person. Their charged Melee becomes unusable, but their Grenade and regular melee still work. Using a Super, a Class Ability, or changing weapons will drop the shard. Using the "primary fire" button will unleash a medium power continuous beam that deals Solar damage. This beam homes in slightly to targets near the center of the screen, an effect better seen when aiming with the weapon. This beam is the only thing that can break the shield of a Disciple's Hourglass, the death of which extends the encounter's Terminal Resonance timer. Dropping the relic will inflict the player with a debuff called Curbed Resonance, which will prevent them from picking up any relic for 30 seconds.