Hyperspace radiation is a deadly radiation found only in hyperspace (as the name suggests). It appears to occupy all of hyperspace and can penetrate any physical material; the only way to block it is with energy shielding.
Hyperspace radiation can be used as a way to detect recent hyperspace jumps, as some radiation seeps out of hyperspace when a ship opens a rift. Hyperspace radiation can also be detected just before a ship exits hyperspace.
Hyperspace radiation has severe effects on organic beings, short exposure generally results in severe burns on skin. Long exposure essentially liquefies organic beings.