Eamonn McCusker of The Digital Fix describes the Mysterons – along with their primary agent, Captain Black – as "the perfect villains", arguing that their menacing voices and green "eyes" helped to make "Captain Scarlet" "more memorable than any of Anderson's other shows". Sarah Kurchak of The A.V. Club believes that the Mysterons marked a departure from the villains of earlier Anderson productions due to their apparent omnipresence and omnipotence. She describes them as "truly, realistically terrifying [...] an unknowable foreign entity capable of the deepest undercover work that could strike at any time," adding that Spectrum's occasional defeats at their hands made them "all the more alarming". Wilkins and Bushwick categorise the Mysterons as an example of the "monstrous and evil" type of Martian commonly seen in film, TV and literature, and rank them second only to the invaders of the H. G. Wells novel "The War of the Worlds" (1897) for malevolence.