Jaruth is mentioned about half a dozen times. In one place Vashishata even prays for his destruction. The story of his birth is in an addendum to Sama Veda. More can be found in the PARSI scriptures. Please do not confuse Parsis with the westren Zoroshterians or Mithraists.

Mithra, btw, is Mitra of RV. Friend. Also known as Surya, the Sun. Parsis are worshippers of Fire and Sun, believe it or not, they too call them Agni and Mitra, not MitHra.