[he nods...and he frowns.]

When we first got to the Digital World, we kept meeting digimon that were being controlled by these black gears that were stuck in them. The gears would make them evil and they'd try to kill us.

And then later, the Digimon Kaiser created these evil rings that would enslave the digimon and make them listen to his commands. The evil spirals were created to control even more powerful digimon, including how they could evolve. So. It's possible.