Epic Dragons are a small family of dragons first introduced in the Epic Level Handbook. Epic dragons are much larger and more powerful than other kinds of dragons, so much so than they are in the Huge size category and have the abilities of adult dragons even as wyrmlings. Epic dragons are usually neutral aligned, but are more likely to be other alignments than other dragons.
Force dragons have a devastating cone of force for their breath weapon and can also use several force based spell-like abilities and are immune to all force effects (in fact they are notable because they are the only monster in third edition to have any defense against force effects). As a force dragon ages, they become harder and harder to see. Juveniles have the effect of the blur spell. Old ones replace this with the effects of the displacement spell. Great Wyrms are completely invisible and displaced. Force dragons have arrogant personalities and prefer to be left alone. Prismatic dragons and a few gods are the only things they have respect for.
Prismatic Dragons are even more powerful than force dragons. Their breath weapon has the effects of the prismatic spray spell and they are immune to all prismatic effects, light based effects, and blindness, and can also use several prismatic and light based spell like abilities. Prismatic dragons are much more social than force dragons and usually neutral alignment.
A third one introduced in Dragon magazine 359. The time dragon is most likely the most powerful dragon and monster ever in D&D history at cr 90 at great wyrm and they can travel through time and control it their breath weapon can age people or send them into the future.
gravewyrm and glacierdark are rarer known epic dragons https://web.archive.org/web/20161101225042/http://archive.wizards.com/default.asp?x=dnd/ei/20040109a and brainstealer dragons are a grey area https://forgottenrealms.fandom.com/wiki/Brainstealer_dragon