Phyresis

Phyresis (progressive generation) is the transformation of a living thing into a Phyrexian creature. After the process, the creature is considered to be compleated.

Phyresis (essentially the replacement of weak mortality with artifice) was developed by Yawgmoth, when he wanted to save the remnants and descendants of the phthisis-inflicted Thran. Phyresis is brought about by glistening oil.