Radstag Radstags are the mutated descendants of the Commonwealth and the Island ' s local population in 2287 . Background . Radstag descended from the common deer in the Commonwealth after their ancestors were exposed to great quantities of radiation in the fallout of the Great War . Due to this longstanding exposure to radiation , radstags , like brahmin , have two heads , less fur , and are sometimes covered in cysts . Characteristics . Biology . Radstag are a genus descended from deer in the Commonwealth . They are dicephalic , or two - headed ; each head is able to swivel and turn on its own . A closer inspection of the heads shows that each head ' s inner eye is blind . Radstag also have two underdeveloped legs hanging limply from their chest , qualifying them as hexapodal . Aside from the ability to bend when a radstag lays down , these legs are nonfunctional . Radstag are usually brown - furred and patchy in places , with small pus - filled cysts from radiation , which most often cover the flanks , feet , heads , and snouts . The cysts more frequently appear on the rabid and glowing varieties and can cover most of the body . Radstag yearling coats are more colorful than those of adult radstag and feature white spotting , similar to the fawns of their deer ancestors . Gameplay attributes . Radstag usually travel in herds of up to four , typically consisting of one radstag and a combination of doe and yearlings . Although radstag are generally non - hostile and will ignore or flee from a player character , companions may attack them if they stray too close . Adult male radstag of each variant can be legendary . Legendaries are much more aggressive than regular variants . One notable difference is a goring attack that will knock the Sole Survivor to the ground and possibly kill them . Variants . Radstag yearling . This is the youngest and smallest of the radstags . They do very little damage and are unable to withstand much damage . Radstag doe . Older and slightly more resilient than yearlings , they are a little more mature and do slightly more damage . However , they can be killed almost as easy as yearlings due to their low health pool . Radstag . This is the standard type of radstag one will encounter when traversing the Commonwealth . Generally shy creatures who will run if approached and won ' t attack unless provoked . They are easy to put down if need be . Albino radstag . Due to a genetic mutation these radstags are distinguishable by their white coloring and are often found as part of a herd . They are stronger than their standard counterparts and will occasionally inflict a poison effect on those they attack . Rabid radstag . This type of radstag has been infected with rabies or some sort of illness impairing its natural reactions . As such they are more aggressive than their healthier counterparts and are more likely to attack as one encroaches on its personal space or without provocation . Glowing radstag . This is the strongest type of radstag encountered in the Commonwealth . They have a higher health pool and have been exposed to so much radiation that their body literally glows with its excesses . When they engage in combat they inflict radiation damage on top of their standard attacks . They are normally seen in groups of 3 or 4 . Erratic radstag doe . A variant of the radstag only found on the Island . Erratic radstag . A variant of the radstag only found on the Island . They look more like water deer found mostly in Asia due to the presence of fangs . Devolved radstag doe . A variant of the radstag only found on the Island . Devolved radstag . A variant of the radstag only found on the Island . Unlike most of the other variants , devolved radstags are immediately hostile to anything but their own kind . Their visual appearance is similar to that of glowing radstags , but they are even stronger and more dangerous . Appearances . Radstag appears in " Fallout 4 " and its add - on " Far Harbor " . Bugs . On rare occasions the glowing radstag may turn invisible during combat .