In the book of Revelation there is a part that describes the souls under the throne, who are these souls?
Actually these souls are not under any throne, but are clearly described as being under an altar - an altar is traditionally a bench or table for sacrifices -
which describes accurately the sacrifice of martyrs for the Word of God.
It is pretty self explanatory - all souls martyred for the Gospel from Stephen (Acts 7) to whomever will be the last person to faithfully die for preaching the Gospel
of salvation right up to the day that Jesus returns with his angels to put an end to the catastrophe of world war (Armageddon).
Preaching the full Gospel of salvation is still not popular and even mocked and ridiculed by many in supposedly "Christian" societies, such as America and Australia.
10 Blessed are they which are persecuted for righteousness' sake: for theirs is the kingdom of heaven.
11 Blessed are ye, when men shall revile you, and persecute you, and shall say all manner of evil against you falsely, for my sake.
12 Rejoice, and be exceeding glad: for great is your reward in heaven: for so persecuted they the prophets which were before you.
Matthew 5:
There may also be included in this population of souls under the altar, prophets from the Old Testament -such as Isaiah and others slain by the Levite Priesthood -
29 Woe unto you, scribes and Pharisees, hypocrites! because ye build the tombs of the prophets, and garnish the sepulchres of the righteous,
30 And say, If we had been in the days of our fathers, we would not have been partakers with them in the blood of the prophets.
31 Wherefore ye be witnesses unto yourselves, that ye are the children of them which killed the prophets.
35 That upon you may come all the righteous blood shed upon the earth, from the blood of righteous Abel unto the blood of Zacharias son of Barachias,
whom ye slew between the temple and the
altar.
Mathew 23:
11 And white robes were given unto every one of them; and it was said unto them, that they should rest yet for a little season, until their fellowservants also and their brethren,
that should be killed as they, should be fulfilled.
Revelation 6: