However, sometimes crossovers are immensely dangerous. -Verses like paraverses have such hostile physical laws that they can tear apart whatever they hit at the molecular, atomic, or subatomic level. Universes full of dangerous materials like antimatter or molten metal can cause huge damage to themselves and to their "targets". In some extreme cases, the differences can be so great that the -verses rip themselves apart in an unbelievably powerful annihilation event, similar to the collision of a particle and its antiparticle.
On some rare cases the colliding verses fully merge resulting in the formation of a single larger one made of the contents of the smaller ones.
It is sometimes thought that collisions between branes created our own universe as well as many others; the validity of this idea is uncertain.