A Tantrika is a dedicated practitioner of Tantra.
Mahendranath used Tantrika (or Tantrik) for the way of life and for the person who lives it. Tantra names a treatise, and the pagan science. They are not one word. A Tantrika is not automatically a Nath of this Order. Kaula is the clan form of that life. Initiation into the INO is a separate transmission. This page names the practitioner.