Twelve Apostles (十二使徒 Jūnishito) are apostles that serves various gods and goddesses. The requirements of becoming a demigod is not clearly defined but becoming an apostle (a type of demigod) is pretty simple; be chosen by a god. All the demigods that showed up in the novel so far are apostles with one exception. The Forest Goddess Yareharun is a sentient forest who became a demigod through sheer evolution alone. She serves no god as her master.
An apostles body regenerates any wound it recieves. Even if their body is torn apart the parts will heal if they are stuck together, in other words they cannot die. It is stated by Giselle, however, that an apostle can be imprisoned or even de-facto eliminated (at least until they ascend) by breaking them into small enough pieces and separating them over large distances, typically by burying said pieces, suggesting they could be destroyed with heavy weapons and explosives, if the parts were separated sufficiently.
In Special Region standard, The Apostles are considered to be extremely dangerous since Rory Mercury and Giselle can tank the entire army of the Empire with little difficulty. Therefore, they are the enforcers of the Gods in keeping the Special Region in check by ''cutting tree branches'' that are grow to big, in this case is anyone attempting to make the advancement in technology and knowledge or putting down pesky races that come from beyond the Gate in other dimensions. However, for modern military standard, they are outmatched against heavy weapons like 50 cal machine gun or explosive weapons since these weapons are strong enough to blow them to pieces to effectively incapacitate them. As the result, most Apostles don't dare to provoke fight with the JSDF, despite they can give modern military some hard times with their superhuman combat power and regeneration ability like in the case of Rory Mercury doesn't want to mess with the whole JSDF and willing to work as an MP under them or Giselle ran away from JSDF's bombardment on her offspring dragons and willing to work as cafeteria worker in Alnus to pay her debt as the bombing traumatizes her. Other powerful forces from other dimension like the Arachnids can overwhelm them with ease as Rory Mercury was overwhelmed by the sheer numbers of Warrior Bugs and was forced to fight for her life. This fact shows that the ability of Apostles to defend the Special Region from inter-dimensional threats is not absolute, Rory Mercury even laments that Hardy was stupid to open the Gate to Japan and she was helpless against the Arachnids without the fire support from the JSDF.
Despite their obviously superior power over normal humans, a many people in the Empire still underestimates them due to their delusional arrogance. The prime example of this is Zorzal and his pro-war supporters since they never take the fact that Rory and Giselle support to the JSDF as serious matter or Zorzal stupidly called his guards and Ogre to kill Rory without realizing how idiotic it is. The another example is during the Siege of Italica, Pina states that Rory Mercury alone can defeat the whole army of defender of Italica but the bandits that attacked the city still try to futilely fight her anyway.
Apostle's power can be stripped from them by their patron gods if the Apostle proves to be too incompetent and the gods just wants to replace someone else new, like the case of Mabel Forn when Zufumus makes her a new Apostle as he tired of the old one.