The Era Corps is the broad term for all of the digimon who work under Era. Most Era Corps members are, perhaps surprisingly, enlisted of their own volition. ... most. There are exceptions to every rule.

Agents
Agents are the "cannon fodder" of the Era Corps; foot soldiers and grunts, they exist to patrol a given area and put down rebellions and keep order so far as it applies to Era's rule. They range from Baby I all the way to Mega, though the vast majority are Adult or Perfect.

Generals
Those in charge of the Agents; few and far between, these are trusted digimon hand-chosen by Era. A select few are even known to have council directly with Era himself, but are rarely privy to his plans beyond what they "need to know" for their jobs.

Reapers
The highest ranking; there are only three in the ranks. Their role in Era's hierarchy is unclear.