Where did they come from? From what period of time? From what circumstances? Just as the angels are holding the four winds of the earth and could have let them go but the angel comes and says hold, don’t let go until we have sealed the servants in their foreheads. The description of this time of God’s wrath is to be poured out is depicted in Jeremiah. You can see the time the angels are being told not to let go just yet. This is speaking of the cup of Gods fury being poured out, the plagues about;

Jeremiah 25:17 Then took I the cup at the LORD’S hand, and made all the nations to drink, unto whom the LORD had sent me:

Then it goes into the description of the destruction of all the nations that is the winds.

Jeremiah 25:31 A noise shall come [even] to the ends of the earth; for the LORD hath a controversy with the nations, he will plead with all flesh; he will give them [that are] wicked to the sword, saith the LORD.
25:32 Thus saith the LORD of hosts, Behold, evil shall go forth from nation to nation, and a great whirlwind shall be raised up from the coasts of the earth.

How big a whirlwind was this? From the coasts of the earth. You can see the angels holding the four winds, east, west, north south.