The third seal can be found in Revelation 6:5-6 and reads as follows…
“When He opened the third seal, I heard the third living creature say, ‘Come and see.’ So I looked, and behold, a black horse, and he who sat on it had a pair of scales in his hand. And I heard a voice in the midst of the four living creatures saying, ‘A quart of wheat for a denarius, and three quarts of barley for a denarius; and do not harm the oil and the wine.’”
>> The 7 seals: background & overview
>> The 4rd seal and the pale horse
>> The second seal and the red horse
White = purity
Red = bloodshed
Black = spiritual darkness and apostasy
This apostasy was in the church from about the third century on down to the sixth century, when the church-state authority was established in 538. Of this time, Philip Schaff, the well-known church historian, says that the elevation of Christianity as the religion of the state involved great risk of spiritual degeneracy to the church.
The prophecy of the apostle Paul was being fulfilled. He said: “For I know this, that after my departure savage wolves will come in among you, not sparing the flock. Also from among yourselves men will rise up, speaking perverse things, to draw away the disciples after themselves” (Acts 20:29, 30).
The Christianizing of the political Roman state amounted, therefore, in great measure to a paganizing and secularizing of the church. The mass of the Roman Empire was baptized only with water, not with the Spirit and fire of the gospel, and thus heathen manners and practices were smuggled into the sanctuary under a new name.
Many of these ancient doctrines, first known to the pagan world and the heathen philosophers, are still carried along by organized Christianity—ideas, customs, rites unknown to the Bible and which were unknown to the apostles and the early Christians.
In summary, In many things during this period the traditions of men began to take the place of the Bible, and the power of the emperor often interfered in the affairs of the church.