Yodh

Letter in Hebrew. Also means 10.

Described as a single letter in the Sepher Yetzirah, one of twelve.

He produced Yod, predominant in Labor, crowned, combined, and formed Virgo in the world, Elul in the year, and the left hand of man. (from the Sepher Yetzirah)

it is the first letter of the name of god, the tetragrammaton. So it is related to Atziluth - The world of Archetypes and to Fire.