Notes on Cornelius as a ShapeshifterA reminder. Cornelius was originally human. He ran afoul of a form-destroying virus which malfunctioned, mutating his body into a genetic hodgepodge of all former hosts of the virus, including himself. Although he's now apparently a monster thing, the virus left his original code intact. Each of his cells contain double DNA strands, one human and one glatni. He's able to express either set at will. But there are lots of catches.Notes on Cornelius as a Shapeshifter by Altalamatox
Just keep in mind that 'unshifted', 'normal', 'actual' Cornelius is glatni, 'shapeshifted' Cornelius is human.
By definition, anything 'magical' that happens in the Network works in conjunction with the nearby dimension, which has different physics. In Cornelius' case, this foots the bill for his change in mass. When he transforms, his shifting field (an area around him pushed drastically nearer the other dimension, temporarily allowing crazy things like all your cells changing at once without killing you) yanks/pushes a whole load of extra matter into/out o