Control Spires

The Control Spires (in Japanese: ダークタワー Dāku Tawā, "Dark Towers") are tall, pitch-black obelisk-like machines that powers both the Dark Rings and the Dark Spirals, and they prevent any Digimon from Digivolving.

The Spires were originally created by the Digimon Emperor to monitor the activity of his brainwashing creations within the areas they were in during his conquest of the Digital World.

Also, Arukenimon uses them to create unliving Digimon.