Doctor Who RPG: Season 1
The Hydrogen Chamber
Hit Capacity: 15
Story Points: 2
This is a device that looks like a big glass cylinder big enough to keep people in. The chamber was activated by valves (Victorian style) and released Hydrogen into the chamber.
A nearby river turned a water wheel to generate current that electrocuted water (via carbon rods) and split them into hydrogen and oxygen. The Hydrogen was then captured within man-sized storage tanks and awaited the second stage.
Once the Plactoras possessed a potential victim, they placed them inside the hydrogen chamber. The valves then released hydrogen into the chamber. The possessed Plactoras then use the hydrogen to draw upon and replicate molecules within the host.