An Osiran war missile was a piece of Osiran technology used to attack targets from astronomical distances.
Using a form of pyramid power as an energy source, the missile could be assembled from numerous components by service robots. It resembled a small pyramid on a platform, but was large enough for a servitor to enter and stand upright. (TV: Pyramids of Mars)
While Sutekh himself was trapped in Egypt, unable to move, he was able to construct a war missile in England with the help of Marcus Scarman's re-animated corpse and a small number of servitors sent through a time-space tunnel.
His plan was to use the missile to annihilate the pyramid on Mars that housed the Eye of Horus, thus freeing himself from captivity. The Fourth Doctor, disguised as a servitor, was able to place a box of gelignite on the ramp of the missile. Sarah-Jane Smith then managed to detonate the box with a rifle shot.
Sutekh immediately noticed the explosion and was able to contain it through sheer force of will, but this required a tremendous effort. The Doctor travelled down the time-space tunnel and momentarily broke Sutekh's concentration by whispering his name. The box exploded, taking the missile with it and forcing Sutekh to alter his plan. (TV: Pyramids of Mars)