A.T. Robertson Commentary Revelation 14:17

"Another angel came out from the temple which is in heaven, he also having a sharp sickle." — Revelation 14:17 (ASV)

He also (κα αυτος). As well as the Reaper on the cloud. This is the fifth angel who is God's messenger from heaven (temple where God dwells). This fifth angel with his sharp sickle is to gather the vintage (18-20) as Christ did the wheat.