Opened (ēnoixen). First aorist active indicative of anoignumi. With the “key” (kleis).
As the smoke of a great furnace (hōs kapnos kaminou megalēs). The plague of demonic locusts is here turned loose. Kaminos is old word for a smelting-furnace, already in Rev 1:15.
Were darkened (eskotōthē). First aorist passive indicative of skotoō, old causative verb from skotos, in N.T. only here, Rev 16:10; Eph 4:18.
By reason of (ek). “Out of,” as a result of (Rev 8:13).