the “living creatures”
These heavenly beings are cherubim and are mentioned by Ezekiel (Ezek. 1-10), Isaiah, and John the Apostle (Rev. 4, etc.).
They are not the same as angels.
Then one of the four living creatures gave to the seven angels seven golden bowls full of the wrath of God… —Rev. 15:7 NASB
They join the elders in the “new song.”
When He had taken the book, the four living creatures and the twenty-four elders fell down before the Lamb, each one holding a harp and golden bowls full of incense, which are the prayers of the saints. And they sang a new song, saying,
“Worthy are You to take the book and to break its seals; for You were slain, and purchased for God with Your blood men from every tribe and tongue and people and nation. —Rev. 5:8-9 NASB
They warn of the danger of divine justice.
I saw the Lord sitting on a throne, lofty and exalted, with the train of His robe filling the temple. Seraphim stood above Him, each having six wings: with two he covered his face, and with two he covered his feet, and with two he flew. And one called out to another and said,
“Holy, Holy, Holy, is the Lord of hosts,
The whole earth is full of His glory.”
And the foundations of the thresholds trembled at the voice of him who called out, while the temple was filling with smoke.
Then I said,
“Woe is me, for I am ruined!
Because I am a man of unclean lips,
And I live among a people of unclean lips;
For my eyes have seen the King, the Lord of hosts.”
Then one of the seraphim flew to me with a burning coal in his hand, which he had taken from the altar with tongs. He touched my mouth with it and said,
“Behold, this has touched your lips; and your iniquity is taken away and your sin is forgiven.”
Then I heard the voice of the Lord, saying,
“Whom shall I send, and who will go for Us?”
Then I said, “Here am I. Send me!” —Isa. 6:1-8 NASB
They associate with the Church in the overthrow of her enemies.
…the twenty-four elders and the four living creatures fell down and worshiped God who sits on the throne saying, “Amen. Hallelujah!” —Rev. 19:4 NASB
They deliver commissions to those who execute them (Ezek. 10:2, 7).
They associate with the elders
in their sympathy with the 144,000 who sing the new song (Rev. 14:3).
They are believed to represent mercy, as distinguished from justice, mercy in its various instrumentalities, and especially as connected with the throne of God—the “throne of grace.”