TimeSerum

TimeSerum is derived from the venom of a now-extinct sub-species of the Gaboon Viper. Its name is something of a misnomer, as it enables one to travel through time only by that laziest of methods, suspended animation.

All known supplies of TimeSerum are under the control of members of the Rosicrucian conspiracy, stored in a vast container concealed beneath Stonehenge which is filled to a capacity equal to 200 Olympic-sized swimming pools (one of which has diving board, or so it is rumoured).

So far as is known, only two people – Alexander Pruitt and Robert Moray – have ever been dosed with it, both of them in the year 1658.