Darkside - The Predacon starship captained by Megatron. It served as the Predacon base for most of the Beast Wars series. Due to trademark issues, the spelling "Darksyde" was used for the Botcon 2006 exclusive story.
Deca Cycle - A Cybertronian unit of time measurement that is approximately thirty Earth days.
Decepticons - The malevolent branch of the Transformers race. Decepticons believe in total domination of the universe and the acquisition of power. Through these ideals, they believe they can become a stronger race.
Deployers - A group of ancient Cybertronian robots resurrected during Beast Machines to serve as weapons for the Maximals.
Destrons - The Japanese term for Decepticons.
Destrongers - A group of Transformers bent on the acquisition of power introduced in the Japanese Car Robots Transformers series.
Diaclone - Takara's robot toy line that preceeded the Transformers.
Diakron - The American releases of some of the Diaclone toys, not marketed under the Transformers name.