Guardian of Light: Lucifer Morningstar

Fragments of dead Guardians materialize in various forms. While it may sometimes appear in a human form like Zero, it may also come as artifacts, weapons, spells or even energies.

When a living form reincarnates, the reincarnated form inherits the important memories of the previous Guardian regarding their mission of existence.

When a non living form is left, it may end up choosing a different path towards their original goals depending upon their forms.

For example, when only the spell fragment or only the energy fragment is left, the person who has that particular spell or energy develops an alter ego, that soon takes over the owner before going berserk for sometime, before finally stabilizing and taking shape of a living robot whose sole purpose is to fulfill their mission handed to them by fate.