Transmat:Species
The Headless Monks were a religious order who believed in listening to their hearts rather than their minds, to the point of having themselves beheaded.
As they were headless, the Headless Monks did not register as living beings. They were also supposedly incapable of being fooled or feeling fear. Despite their lack of heads, the Monks were able to detect where other beings were. They could fire energy blasts from their hands, as well as channelling that energy into the swords they carried.
The show's been on forever. Some species names are simply going to get reused. One of the most obvious are the Vogans. Most fans remember the Vogan from season 12's Revenge of the Cybermen. But there's also the [[Vogan (The Vogan Slaves)|Vogans that plagued the Third Doctor… ]]
If you like alien species that are based on Earth animals, you're in luck. All you have to do is go to the page of an Earth mammal and check out the "looks like" box. For instance, if you wanna know what aliens look like elephants, just go that pachyderm's page and find yourself a breadcrumb at the top of the page.