The Dalek race, which first appeared in the show's second serial in 1963, are "Doctor Who"s oldest villains. The Daleks are Kaleds from the planet Skaro, mutated by the scientist Davros and housed in mechanical armour shells for mobility. The actual creatures resemble octopuses with large, pronounced brains. Their armour shells have a single eye-stalk, a sink-plunger-like device that serves the purpose of a hand, and a directed-energy weapon. Their main weakness is their eyestalk; attacks upon them using various weapons can blind a Dalek, making it go mad. Their chief role in the series plot, as they frequently remark in their instantly recognisable metallic voices, is to "exterminate" all non-Dalek beings. They even attack the Time Lords in the Time War, as shown during the 50th Anniversary of the show. They continue to be a recurring 'monster' within the Doctor Who franchise, their most recent appearance being the 2021 episode "Revolution of the Daleks". Davros has also been a recurring figure since his debut in "Genesis of the Daleks", although played by several different actors.