Fighting-Machine

Based off the alien invaders from H. G. Wells' The War of the Worlds, the fighting-machines were race of creatures genetically engineered by Missy on Planetoid 50.

Biology
As described by Missy, the creatures were grown using whatever she found in her TARDIS' bio-filters. Unlike the invaders from Wells' story, these creatures were immune to all Earth diseases. The Tenth Doctor found that they had nothing in common with the Ice Warriors. (AUDIO: The Martian Invasion of Planetoid 50)

History
When suffering from a retro-regeneration crisis, the Master attempted to focus their mind and tried to finally finish The War of the Worlds. Inspired by the book, the Master recreated the events on Planetoid 50, abducting inhabitants from 19th century London, including the Paternoster Gang, to serve as hapless victims. The Master bestowed Time Lord technology upon the Martians, including a beam that briefly stablised their form, though causing them to regenerate into Missy, an incarnation from their future.

When the Doctor, suffering from the same degeneration crisis, arrived on Planetoid 50, being struck by the Martians' weapon caused him to likewise regenerate into a future form, the Tenth Doctor. After freeing the Paternoster Gang, the Tenth Doctor had them lure the Martians all in one place. Stealing and repairing the Master's Tissue Compression Eliminator, the Doctor shrank the fighting-machines to only a few feet in height. After returning the Paternoster Gang to their own time, the Doctor, now changed into the form of the Third Doctor, set the fighting-machines free on Mars in the planet's ancient past. (AUDIO: The Martian Invasion of Planetoid 50)