Digimon X-Evolution

The Digital World is becoming so overpopulated that the super computer Yggdrasill who governs the Digital World can no longer handle it.

Its solution is Project Ark: to wipe out most of inhabitants with the X Program.

Yggdrasill chooses a very small percentage to be moved to a new Digital World and then proceeds to destroy the old one.

Some Digimon who were not chosen survive anyway and they move to the new world with a rare gift known as the X Antibody; this antibody changes their appearance and makes them more powerful, while at the same time making them immune to the X Program.

No longer in control, Yggdrasill uses the Royal Knights to destroy these X-Digimon, who are outcasts in the new Digital World.