Quad magnetism

Quasi-magnetism was, according to the Fifth Doctor, "the only force known to shield anti-matter." It was created when a Q star burnt out. Omega once took advantage of quasi-magnetism, hiding behind it in the area of space known as Rondel or the Arc of Infinity. When the Doctor and Nyssa passed through the area, the TARDIS sensors were able to detect quasi-magnetism. (DW: Arc of Infinity)