Thelema can be looked at as a path of return to nature (Nuit, Babalon, or Isis), from out of death (Osiris), by means of the spirit of erotic destruction (Apophis or the HGA). It’s the IAO formula in reverse.
The spirit of erotic destruction takes the form of Baphomet in Liber XV. Baphomet is the Lion-Serpent (HGA) that destroys the destroyer (death or limitation) by means of love. Paradoxically we invoke annihilation upon ourselves so we may live for the first time.
This mystery is presented as a cultic rite in Liber XV.