Z-battery

The Z-battery was an object harnessing Z-radiation which was possessed by the Third Doctor before leaving it behind in UNIT HQ after failing to use it to jump start his TARDIS during his exile. The Decayed Master plotted to combine the radiation within it with O-radiation on Oseidon to create ZO-radiation only to be thwarted by the Fourth Doctor. (AUDIO: The Oseidon Adventure)