Q: Who was Matsyendranath?

A: Matsyendranath (aka Macchagnanath) (circa 900 A.D.)

He is associated with the foundation of the Kaula school of
tantra. In a list of the gurus associated with the worship
(puja) of the Goddess Kali, his name, along with his disciple
Gorakhnatha, features prominently.

In the Kaulajnananirnaya Tantra (characteristics of Kaula knowledge),
the god Shiva describes the self as one who is eternal,
without decay and impurity. All that is created comes
through the three Shaktis (female energies) of Iccha (Will),
Jnana (Knowledge) and Kriya (Action). There are eight basic
mantras and these, through their combination, give birth
to 64 Yoginis (female yogis), which are in the eight chakras.

The Natha, being free, may behave like a child, a madman, a
king, a hero or a naked person. He or she can do whatsoever
is willed (Sveccha -- according to own will). The root
of freedom is the mantra Hamsa uttered 21600 times a day with
the breath.

In Nepal, Matsyendranath is accorded great honour and identified
with Avalokiteshvara, seated on the Mount Potala. He is still
to this day worshipped as the Red Lokeshvara of Bugama. Said
to have revealed the Kaula knowledge on an island called
Chandradvipa, he then imparted it to others at Kamarupa in
Assam.

The Shabara Tantra describes him as one of the 12 Kapalika
Gurus, renowned as a knower of yoga. In the lists of the
Siddhas of Tibetan Lamaism, Matsyendranath is accorded first
place.