Alternate spellings of the name were Epialos (Ἠπίαλος), Epioles (Ἠπιόλης), Epialtes (Ἐπιάλτης) or Ephialtes (Ἐφιάλτης).
Epiales was probably numbered amongst the Oneiroi (Dream-Spirits) and thus one of the sons of the goddess Nyx (Night).
[1]"The words epialos, epiales and epioles denote (1) the feverish chill (2) the daimon who assaults sleepers.
Homer and most writers have epioles with the e; the form in -os means something different, namely the feverish chill .
Apollonios says that Epialtes itself (the nighmare daimon) is called Epiales and by a change of a to o Epioles.