Definition taken from www.blue-bottle.co.uk/trans.htm

Iosis is the final stage of Alchemical Transformation and is also known as the "Purple Phase".

At this stage everything comes together. It represents embodiment of the spirit where everything comes from the One and returns to the One. It occurs as a reddening of the matter, and ultimately results in the production of the red tincture or elixir. It is where heaven and earth meet and marry, bringing about a wholeness and representing both marriage and death. It is the gold stage, symbolised by a red sun or a red lion, the yolk of the egg or a garden of endless fertility. It is also represented by a cherubic Mercurius child introducing us to the idea that humanity is a microcosm that reflects the Macrocosm of the Divine. Its ultimate symbol is that of the hermaphroditic Uroboros, the great snake swallowing its own tail, signifying completion and encircling.

The process of change from leukosis to iosis was symbolically represented by the coming together of the red king and white queen - the chemical wedding. Hence the final goal of the production of the red elixir or philosophers’ stone, represents a union of both male and female - a hermaphrodite of nature.