ARKE (or Arce) was the messenger of the Titan gods and the twin sister of the rainbow-goddess Iris. She may have been associated with the faded second rainbow sometimes seen in the shadow of the first. During the Titan-Wars the two goddesses served on opposite sides--where Iris became the messenger of the Olympian Gods, Arke assumed the role of messenger for the Titanes. At the end of the war, Zeus stripped her of her wings, and cast her into the Tartarean pit along with her masters.
According to Hesychius the messenger of the Titan gods in the old Titanomachia epic attributed to Eumelus, was named Ithax or Ithas.
ARCE (Arkê), a daughter of Thaumas and sister of Iris, who in the contest of the gods with the Titans sided with the latter. Zeus afterwards punished her for this by throwing her into Tartarus and depriving her of her wings, which were given to Thetis at her marriage with Peleus. Thetis afterwards fixed these wings to the feet of her son Achilles, who was therefore called podarkês. (Ptolem. Hephaest. 6.)
Source: Dictionary of Greek and Roman Biography and Mythology.
Ptolemy Hephaestion, New History Book 6 (summary from Photius, Myriobiblon 190) (trans. Pearse) (Greek mythographer C1st to C2nd A.D.) :
"It is said . . . that he [Akhilleus, Achilles] was called Podarkes (Swift-Footed) by the Poet [i.e. Homer], because, it is said, Thetis gave the newborn child the wings of Arke and Podarkes means that his feet had the wings of Arke (Arce). And Arke was the daughter of Thaumas and her sister was Iris; both had wings, but, during the struggle of the gods against the Titanes (Titans), Arke flew out of the camp of the gods and joined the Titanes. After the victory Zeus removed her wings before throwing her into Tartaros and, when he came to the wedding of Peleus and Thetis, he brought these wings as a gift for Thetis."
- Ptolemy Hephaestion, New History - Greek Scholar C1st-2nd A.D.
- Photius, Myriobiblon - Byzantine Greek Scholar C9th A.D.