The power (h exousia). As in Exodus 2:26 ; Exodus 6:8 . This power of the horses is both in their mouths (because of the fire, smoke, brimstone) and in their tails, "for their tails are like unto serpents" (ai gar ourai autwn omoiai opesin). Associative-instrumental case opesin after omoiai. Opi is old word for snake ( Matthew 7:10 ). Having heads (ecousai kepala). Feminine present active participle of ecw, agreeing with ourai (tails). With them (en autai). Instrumental use of en. Surely dreadful monsters.