A.T. Robertson Commentary Revelation 17:12

"And the ten horns that thou sawest are ten kings, who have received no kingdom as yet; but they receive authority as kings, with the beast, for one hour." — Revelation 17:12 (ASV)

Which have received no kingdom as yet (οιτινες βασιλειαν ουπω ελαβον). Second aorist (proleptic and prophetic) active indicative of λαμβανω. The heads are emperors and the horns are kings (both called βασιλεις).

As kings (ως βασιλεις). Compared to kings (see ως in 1:10; 4:6; 9:7; 13:3; 14:3; 16:21) without identification with the emperors, though succeeding them with "quasi-imperial powers" with the beast.

For one hour (μιαν ωραν). Accusative of extent of time, and that a brief time (18:10,16,19) in comparison with the beast (13:2).