Lodestone

The Lodestones were a type of time travel technology used by the Osirian civilization.

They took the form of an Egyptian sarcophagus and were entraces into a time space tunnel. When activated, the coffin shaped device loses its stone form and becomes a visible doorway with energy spiralling in its form.

One such lodestone threw The Doctor's TARDIS of course and allowed Marcus Scarman to travel to 1980 in order to destroy Sutekh's prison thus freeing his master. (DW: Pyramids of Mars)