The One who is always partially awake within.
She is the state where consciousness is partially awake, on the threshold of transitions. Transitions from material to spiritual, unreal to real, unconsciousness to subconsciousness, dreams to divine guidance.
She represents that state of balance between all dualities, half-wakefulness and thresholds of transitions, where surrender to Her leads to quiet unfolding of Her nature.
She is known to always reside at a yogic trance within the Sadhakas which may surface as an Avesham, even without their own knowledge.
There are many lores of Kaalika operating and embodying her sadhakas and getting dharmic karya done. The more the Bhairava Tattwa, higher the ability to retain her Shakti.
Hence the name, Tandra ca.