H is for... Headless Monks

A religious order - the Order of the Headless - the Monks believed that the mind was the seat of evil (or potential evil), and so they opted to dispense with their heads and listen to their hearts instead. Their heads were kept in boxes in special vaults, though older ones were simply left on shelves or in pits. The heads retained some life, whilst the Monks themselves did not register as being alive. Despite them not having any brain, ears, nose or mouth, they could sense their surroundings without any problem, and could even chant. One such chant was their "death chant", used when they went into battle. Their favoured weapons were laser-enhanced swords, and their favoured means of dispatch was to behead their victims.
The Monks joined forces with the Kovarian branch of the Church, when it abducted Amy Pond in order to obtain her baby. The different faiths represented on the Demons Run asteroid were expected to exchange knowledge, and this meant for some becoming Headless Monks themselves.
It was generally a capital offence to see beneath the hood of one of the Monks, but those on Demons Run obtained special dispensation from the Papal Mainframe to do this. The Doctor disguised himself as a Monk to infiltrate the asteroid, and then sowed dissent amongst the rival faiths - setting them fighting amongst themselves. When the base personnel were forced to flee, the Monks were able to remain behind due to them not appearing on lifeform scanners. They were eventually killed by the Doctor's associates.
Previously, the Doctor and Amy had visited a museum belonging to the Order - the Delirium Archive, and later, the Doctor visited one of their crypts - the Seventh Transept - in search of the still-living head of Dorium Maldovar, who knew some of the Order's secrets after doing business with them on many occasions. The Doctor was accompanied by a member of the Kovarian branch - Gantok. He was killed when he fell into a pit of ravenous skulls.

Appearances: A Good Man Goes To War (2011), The Wedding of River Song (2011).