The demonic army Emperor Ganishka raised using magic. Daka are born by corrupting human fetuses using an enslaved mass of chained Apostle and magic. By sewing a huge mass of apostles together and dropping live, pregnant human women inside of the result, the Daka are born in the Astral realm, within the Apostles, through their mothers' stomachs, killing them in the process. They are fed human meat (their own mother) and live only to serve their master, Ganishka.  They resemble misshapen humans with horns and large teeth. They fight with spears made of twisted horn. Despite their fearsome appearance, they have not been shown to be much more dangerous than ordinary soldiers- especially not when facing Guts or Griffith's Apostle. When a Daka is slain, its dead body will slowly turn into that of a human.
It is unknown if they can act out on their own since sometimes Kushan magic users are around and if the latter is killed the former wakes up from mind control similar to those of the Pishacha.