A traveler from another world who had their only kin taken away, forcing them to embark on a journey to find The Seven.

The Traveler's personality is determined primarily by the player themselves through dialogue options.

Their personality can range from stoic, humble and helpful to boastful, lazy and short-tempered. Regardless of the player's in-game decisions, all of the playable characters view the Traveler in a positive light. There are instances of single speech options or similar options which give a glimpse at their personality overall. They are, for example, observed by Paimon as not believing the gods are any more worthy of unearned respect than mortal inhabitants of Teyvat. They also are pointedly uninterested in getting involved with each nation's troubles and primarily only concern themselves with finding out their sibling's whereabouts. Their response to Morax's "death" was initially to simply leave, both to avoid suspicion and seemingly a level of apathy considering the circumstances of their arrival on the world.

Both siblings have blonde hair, fiery-gold eyes and slim builds with pale skin. They physically have human appearances, but they have an extremely long lifespan, having been alive for at least 500 years at the start of the game.During their fight with the Unknown God, both siblings had glowing white clothing and yellow wings. After, the player's chosen sibling will lose their white light — Aether's will turn a glassy black and Lumine's will be dull, but these pieces will light up once again after resonating with a Statue of the Seven. The color will change based on which element they are resonated with.

Aether

Aether is taller, has a more vibrant, saturated shade of yellow-blonde hair than his twin. His hair is cut at somewhat medium length with uneven bangs at the front with waist-length braided hair at the back.

Aether's color scheme primarily consists of black, gold, and white. He wears a dark brown breastplate vest with gold and black accents baring his midriff and adorned with a diamond ornament,  a white scarf clamped with a gold clip, and a white two-tailed cape lined with golden embroidery. He wears dark hakama-like pants, dark brown gloves and black boots accented with gold.

Aether and Lumine arrive in Teyvat, yet for some unknown reason the player's chosen sibling does not wake and remained asleep for an unspecified amount of time. The Traveler's sibling eventually manages to wake them up and says that they should leave, with both twins witnessing the destruction of Khaenri'ah. However, an Unknown God, describing herself to be the Sustainer of Heavenly Principles, blocked their way. A fight ensued and resulted in one of the twins getting consumed by red cubes from the Unknown God, and the other trapped in a seal which caused them to lose their powers. Five hundred years later, the Traveler wakes up, separated from their sibling, and stranded. One day they accidentally fish out Paimon from a lake, saving her from drowning.

More can be found at Traveler genshin Wiki