Arctus

Arctus (Greek: Αρκτος, meaning "Bear") was the youngest of the Horae. She was the daughter of Chronos and Ananke. In some versions she is considered a daughter of Helios.

Myths & Legends
She represented the time of night. Based off of her name, she may have connections to the Ursa constellation. She is sometimes depicted as a maiden with a dress in a dark violet colour.

Accompany Helios
The Horae are known to accompany Helios (sometimes Apollo) into the sky, and take care of the horses that pull the chariot of the sun. As mentioned in the poem below, they would assist in taking the horses out to pasture, taking Helios' corona off his head, and putting away the chariot.

"'Far on the sloping margin of the western sea sinking Sol (the Sun) [Helios] had unyoked his flaming steeds, and laved their bright manes in the springs of Oceanus . . . and the swift-striding Horae (Hours), who strip him of his reins and the woven glory of his golden coronet, and relive his horse's dripping breasts of the hot harness; some turn the well-deserving steeds into the soft pasture, and lean the chariot backward, pole in air.'"

"- Statius, Thebaid 3. 406 ff (trans. Mozley) (Roman epic C1st A.D.)"

Handmaiden of Harmonia
Dysis was also specifically mentioned in the poem Dionysiaca as a protector and handmaiden of the hall of Harmonia (in the vault of heaven), who stood at one of the four gates. She attended to the side towards the North Wind, Boreas. "'Handmaids [i.e. the Horai (Hours)] protected this dwelling on all sides, a round image of the universe : the doors were allotted--Anatolia (Rising) was the maid who attended the East Wind's (Euros') gate; at the West Wind's (Zephyros') was Dysis (Setting) the nurse of Selene (the Moon); Mesembrias (Midday) held the bold of the fiery South (Notos); Arktos the Bear was the servant who opened the gate of the North (Boreas), thick with clouds and sprinkled with hail.'"In some versions it seems she was depicted as a bear, or simply had the title of one.