"Then the angel took the censer, filled it with fire from the altar, and hurled it on the earth; and there came forth peals of thunder, rumblings, flashes of lightning and an earthquake. Then the seven angels who had the seven trumpets prepared to sound them." (Revelation 8.5-6)
"The angel took the censer," filled it with coals from the altar and dashed it on the ground. The Altar in the Temple in Jerusalem had, "three separate piles of wood on top of it. The largest of these was where all the portions of the sacrifices were burned, the second fire provided the coals for the Altar of Incense within the sanctuary, and the third was the "perpetual fire" which constantly burned on the altar." No sacrifice was placed on it, and no coals were taken from it.
This altar existed solely to fulfill the commandment that there be a perpetual fire, as the Law states, "And a fire shall burn there on the altar constantly, it shall not be extinguished." There was no commandment regarding the type of wood to be used except that the Rabbis forbade the use of olive wood and grape vine wood, as these did not burn well and needed to be conserved because of their commercial value to the people."
This is the prelude to the "peals of thunder, rumblings, flashes of lightning and an earthquake" which are the introduction to more terrors. The picture is similar to the vision in Ezekiel 10.2, in which a man in a linen cloth, maybe the censor angel, takes coals from between the cherubim and scatters them over the city. It is also like a vision of Isaiah 6.6 in which the prophet's lips are touched with a live coal from the altar.
The Revelation censer angel brings coals to introduce new woes. "The prayers of the saints return to the earth in wrath." says H.B.Swete. The idea in John's mind is that the prayers of the saints will bring vengeance through the angel upon those who had tortured and killed them. "The seven angels," known as the angels of the presence, are sometimes thought to be the names of the seven archangels.
The archangels' names according to Enoch and the Apocryphal Book of Tobit 12.15 are traditionally known as Uriel, Raphael, Raguel, Michael, Saraqael, Gabriel and Remiel. The fact that they were called "the angels of the presence" means that they enjoyed the special honor of being in the close proximity to God himself. In an oriental court, it was only the most favored courtiers who had the right at all times to be in the presence of the king. To be a courtier was a special honor anyway. To be in the presence of the king not only meant special honor and rewards but immediate readiness to be dispatched on an errand or service elsewhere.