Realm Travel

Traveling between Realms is not only possible, it has been achieved multiple times by different realities! The process requires an astronomical energy expenditure. This is usually achieved through machines on an galactic scale or through the use of powerful and unstable magic. The only safe means of traveling between dimensions makes use of interdimensional portals. The portals persist after being created as a sort of tear or incision in the fabric of realities. These tears require an additional expenditure of energy to seal and depending on how or where they were formed are often difficult to detect.

Passing through the portal and traveling into another realm wraps the traveler in a bubble of their own reality that protects them from any differences in physics between their realm and the other.  

Multiple portals between two realms slowly results in Realm Bleed, also called dimensional merging. Over time the laws of physics and magic between the two realities become one definitive set of laws and the two realms become one. Once the process is complete it cannot be reversed. Closing portals between realms can reverse these effects.