Of all of the seals, trumpets and bowls, the fifth seal is unique, because the breaking of it does not cause any wrathful consequence upon the earth, and it is solely concerned with Believers as God's plan of judgment unfolds.

When the Lamb broke the fifth seal, I saw underneath the altar the souls of those who had been slain because of the word of God, and because of the testimony which they had maintained; and they cried out with a loud voice, saying, "How long, O Lord, holy and true, will You refrain from judging and avenging our blood on those who dwell on the earth?" And there was given to each of them a white robe; and they were told that they should rest for a little while longer, until the number of their fellow servants and their brethren who were to be killed even as they had been, would be completed also. (Rev 6:9-11)

When Jesus breaks the fifth seal, the following observations can be made:

The apostle John can see the souls of Believers who were martyred because of their faith in and testimony of God. Since this was before their rapture (1 Thess 4:14-17; Rev 14:14-16), the apostle saw disembodied souls.

Who are these martyrs? They are Messianic Jews and Gentile Believers who died for their faith during the Great Tribulation (Rev 6:9-11; 7:9-15).

These martyred souls were being released from underneath the altar in the heavenly Temple of God. To gain a sense of the altar in the heavenly Temple of God, some information may be drawn from the earthly Temple.

Of the two alters that the earthly Temple had, the Alter of Incense was the one inside the Temple, in the Holy Place, and outside the Holy of Holies housing the Ark of the Covenant. Because it was overlaid with gold, it was known as the Golden Alter (Ex 39:38; 40:5; Num 4:11), and it was shaped in a square with four horns at each corner and considered "most holy to the Lord (Ex 30:1-10).

The altar in the heavenly Temple of God was described as the four horned golden altar (Rev 8:3; 9:13).

The incense, made to an exclusive formula (Ex 30:9, 34-38), was burned after the morning and evening sacrifices. Like animal offerings (Ex 29:15-18), grain offerings (Lev 2:1-2, 4-9), and drink offering (Num 15:1-13) burnt on the altar outside of the Temple (Ex 20:24-26; 27:1-5), which produced a soothing and appeasing aroma to the Lord (Gen 8:20-21), this incense recipe emitted a fragrance that also soothed God's wrath. Functioning in a similar fashion, the psalmist portrays incense as symbolic of the prayers of Believers (Ps 141:2).

In the heavenly Temple of God, the four living creatures and the twenty four elders are each holding "golden bowls full of incense, which are the prayers of the saints" (Rev 5:8). In the context of the heavenly Temple of God, the saints here refer to saints who died in the Great Tribulation (Rev 6:9-11; 7:13-15). While this suggests that the recipe for the incense in the heavenly Temple of God is the prayers of the tribulation saints in the heavenly Temple, elsewhere incense is mentioned as the prayers of the saints (Rev 5:8; 8:3) that suggest it includes the prayers of saints who are still alive on earth.

The martyred souls sought justice and appealed to God's punishment of the wicked (Deut 32:35-36; Rom 12:18-21; Heb 10:30-31). These martyred souls would be recognized for their love and service of God (Rev 7:9-17).

Upon their release from underneath the altar, the martyred souls were given a white robe (Rev 6:11), which represented the righteous acts of the saints (Rev 19:8). This clothing is reminiscent of Jesus' Parable of the Wedding Banquet (Matt 22:1-14), and later the wedding banquet actually occurs in heaven (Rev 19:7-8)!

It is significant to observe that when the tribulation saints were given their white robes, they were told to rest "for a little while longer, until the number of their fellow servants and their brethren who were to be killed even as they had been, would be completed also" (Rev 6:11). This suggests that all of the remaining tribulation saints will be killed soon.

In the third interlude just prior to the seventh seal, a "great multitude which no one could count, from every nation and all tribes and peoples and tongues" of tribulation saints are presented before the throne of God and before Jesus Christ praising both with palm branches (Rev 7:9-10).

At the end of the sixth trumpet, the apostle John reports that all of the survivors of the plagues were not repentant (Rev 9:20), which suggests that before the seventh trumpet is sounded, all Believers are likely dead.

Using a chart to record these observations, the existence of the tribulation saints would look like this: