it. Ellipsis to be supplied by "the lamb" from verse preceding (App-6).
souls. Hebrew, plural of nephesh. Verse 15, singular. See App-13.
eating. Hebrew mouth. Figure of speech Metonymy (of Cause), App-6, mouth put for what is eaten by it.
lamb. Repeated at beginning of next clause in the Figure of speech Anadiplosis (App-6) for emphasis.