One of the few families who mostly escaped Sombra’s genocide of the Crystal City, those of House Shimmer were once among Queen Rhodonite’s closest advisors, and the trusted protectors of the Sun Stone – a mysterious artefact holding great power.
Sunstone Shimmer is one of the very last members of the House, descended directly from the last Guardian of the Sun Stone. Her family maintained as much of their blood purity as possible throughout the ages, allowing her to display most traits associated with the near-extinct crystal ponies (she lacks the mane gradients and transparency).
Sunstone gained the nickname of ‘Sunset’ due to the perceived end of her lineage, and by extension, that of all crystal ponies. She is much younger than her Equusian counterpart, being a few years younger than the Cutie Mark Crusaders, as opposed to several years older. - Her parents died of a flu epidemic that swept Equestria when she was around ten years old, prior to gaining her Cutie Mark for a talent in magic. With no other family members to take her in, Sunset fled with nothing but a set of saddlebags full of food and bits, and the Sun Stone around her neck, and has resorted to stealing to survive ever since.