Below, you can find the full FFXIV: Shadowbringers item info for the Soul of the Gunbreaker item. This item is a Soul Crystal and is usually a crafting material or the product of a craft. Sometimes it can be dropped from a monster or found in a chest.

Soul of the Gunbreaker - Amulets - Items

Soul of the Gunbreaker
Soul Crystal

GNB

Level: 30 		Item Level: 30

NPC: FFXIV Gil 0

Upon the surface of this multi-aspected crystal are carved the myriad deeds of gunbreakers from eras past.