Monster Virtualization is the process of Monsters spawning. There are variety of ways that monsters spawn.

Standard Virtualization

Standard Monster Virtualization is by far the most common form of monster virtualization shown. This is usually run by X.A.N.A.. The monster's vector lines appear, and then the area between the vector lines is filled, and the monster either falls to the ground or flies.

Spawning From The Ground

This was only shown in "Mister Pück" in the Ice Sector. This is a way by which Bloks can spawn. Basically, the ground cracks, and monsters crawl out of said cracks.

Manta Hatching

Mantas can spawn from the outer walls of Sector Five. This seems to follow a time delay cycle. During "Tidal Wave", a similar phenomenon occurred with a Creeper.

Manta Mine Laying

Mantas can lay Flying Mines. The largest occurrence of this was in "Cold War".

Monster Materialization

On two occasions, X.A.N.A. materialized monsters via the Scanners. This first happened in "False Start", where X.A.N.A. materialized a small army of Kankrelats. Later, in "A Bad Turn", three Krabs were materialized, though doing so caused the scanners to be destroyed.

Monster Spectres

On a later occasion in "Hard Luck", via adapting the teleportation procedure used by the Lyoko Warriors, X.A.N.A. created monster Spectres. These were in the form of Kankrelats to New Mexico Research Facility.

Kolossus Virtualization

The Kolossus has been virtualized thrice and they had the same, albeit unique, procedure. In this variation, hundreds of Replikas start allocating their respective resources to the creation of the Kolossus. The first usage of this revealed the sheer number of replikas to the Lyoko Warriors, which led Jeremie to develop the Anti-X.A.N.A. Program.