Yesod
Yesod, Foundation

He chose three letters
from among the Elementals
[in the Mystery of the three Mothers
Alef Mem Shin]
And he set them in His great Name
and with them, He sealed six Extremities.
…Nine: He sealed "south" and faced to the right
and sealed it with י ו ה
— Sepher Yetzirah

Yesod is the Astral Light, the Storehouse of Images, the coiled energies of Kundalini, the cycling energies underlying matter. It is Ego, the reactive or emotive portion of I.

PlanetMoon (Levanah, ‎לבנה‏)
NameYesod, יסוד, foundation
Divine Name Shaddai El Chai, שדי אל חי
Archangel Gabriel (גברי־אל‎),[1] Prince of Change and Alteration
Angelic orderKerubim (also called Order of Angels)
Tarotthe four nines
ColorViolet[2]
Yetsiratic Attribution[3] Pure Intelligence (Pure Consciousness, Sekhel Tahor), because it purifies the Numerations, it proves and corrects the designing of their representation, and disposes their unity with which they are combined without diminution or division. (Hint: 9 = 32.)
TriadSubconscious

[1]From גבר, to be strong, this name means Strong One of God.
[2]Colors listed are in the Queen scale. The complete set of colors are:
Indigo - King scale (Atziluth)
Violet - Queen scale (Briah)
Very dark purple - Emperor scale (Yetzirah)
Citrine, flecked azure - Empress scale (Assiah)
[3]From the 32 Paths of Wisdom, often printed as an appendix to Sepher Yetzirah.
[1]From גבר, to be strong, this name means Strong One of God.
[2]Colors listed are in the Queen scale. The complete set of colors are:
Indigo - King scale (Atziluth)
Violet - Queen scale (Briah)
Very dark purple - Emperor scale (Yetzirah)
Citrine, flecked azure - Empress scale (Assiah)
[3]From the 32 Paths of Wisdom, often printed as an appendix to Sepher Yetzirah.