So! Here’s ze Material Plane. S’chillin. Zat is a sweet Material Plane you might say. Wraong!
Portals are rifts of energy that form when two Planes’ energy or leylines cause fissures to erupt throughout the interplanar fabric. Portals can connect two or more planes at locations that shift slowly (on the order of weeks per inch), and can allow objects or beings to travel between the linked planes, which accounts for the presence of Outsiders on the Material Plane. Portals are crazy shit, man. They’ll fuck you up. They emit harmful radiation to those who stand too close – the particles that are generated when the empty space between planes is split are impossible to comprehend and can have unpredictable and bizarre effects on living organisms.