Dark Mother Kali Maa
In RIG VEDA 7.72.12: mother Kali is the deity who slices the Ego and takes us into Immortal life or Moksha as in the Mahamritunjaya Mantra to Rudra. This mantra appears in RV 7.72.12 long before its appearance in Krishna Yajurveda (also known as Taittriya Samhita)
As per Mukunda upashnid 2.1 Kali is mentioned as one of the seven tongues of Agni
"Is Kali, my Divine Mother, of a black complexion?
She appears black because She is viewed from a distance
But when intimately known She is no longer so
The sky appears blue at a distance, but look at it close by
And you will find that it has no color
The water of the ocean looks blue at a distance
But when you go near and take it on your hand, you find that it is colorless".