Gems can fuse. Fusions are like sharing a new body with someone else including their emotions, sensations, etc- this does NOT mean they know their past. Fusions will feel each other's desires, emotions, etc. Fusion's appearances are based on how stable it is, how they interpret each other, and a mix of one's color palettes and personality to depict their weapons and such. A gem can puff if harmed but have no blood (they are hard light projections from their gems) and will retreat into their gem until reformed with their wanted appearance and appear as a white, blank silhouette before finishing- they can change their accessories, clothing, hair, everything except their color palette and gem placement.