Devil Z is a Destron entity which posseses vast power, but no true body of its own. It resembles a human embryo, encased in a glowing ball of energy.
Flashbacks
Thousands of years ago, Devil Z stole the 9 Godmaster Transtectors from the Z Nebula and placed them on Earth, in order to soak up the energy needed to power them.
Modern day activity
Devil Z came to lead both the Destrons stranded on Earth and a Destron-worshipping human cult. Lacking a physical form, it laid low until Black Zarak came to Earth. Devil-Z possessed Black Zarak's body, killingScorponok in the process. Devil-Z (now calling himself Devil Zarak) used his new powers to turn the Darkwings into true robots, unleashing them upon the Earth in order to destroy humanity's spirit. Devil Zarak was eventually lured into a final battle with God Ginrai. After taking heavy damage from the Autobot leader, Devil Zarak shifted into a new, powerful two-headed serpent mode. The serpent mode proved unable to stop God Ginrai's Fire Guts attack, however, and Devil Zarak was destroyed.
Zone
Black Zarak was revived as a thrall of the Destron demon Violinjiger. Devil Z may or may not have been revived, as well.