Lore about MDM Giratina:

Before infection happened, MDM Giratina used to have Altered form and Origin form. MDM Giratina greeting to pokemons... Until Infection happened, some of pokemons getting infected to become monstrous and terrifying. MDM Giratina tries goes back to its Distortion World but Something worse happened to MDM Giratina... MDM Giratina was running with 6 legs then MDM Giratina suddenly floating in air as 6 legs slowly disappeared to losing Altered form, but MDM Giratina begins to gain spikes on its body. It gains 12 eyes as well. MDM Giratina no longer altered form; MDM Giratina is now completely stuck in its origin form. But something unusual happened, it gains shadow form. It changes to shadow form, but it gives off nightmare aura caused some of pokemons feared MDM Giratina. MDM Arceus got worried about that, MDM Arceus decide to banish mdm giratina to its distortion world after that.

MDM Giratina trapped in its distortion world for very long time, MDM Giratina getting filled of rage and slowly become mindless monster