Good question. The articles on the site are set in the year 8170 F.R., which means that three out of the seven Lords of Sin have been slain.
Thuldin the Fallen the Lord of Pride was killed. He ruled Kale.
Brathelathor the Lord of Lust was killed. He ruled Kelerak.
Saithith the Lord of Gluttony was killed. He ruled Daven.
Still alive and very much kicking: Garlgax the Lord of Envy, ruler of Orland.
Bork the Lord of Sloth, ruler of Zeland.
Aklystykor, the Lord of Greed.
Nabarus the Lord of Wrath, ruler of the kingdom of Farland.
That means that the three western-most kingdoms are liberated but teetering on the brink of an invasion that will take away their liberty. The four eastern most kingdoms are still occupied. The Border River is the literal border, the front of the war, so to speak. This gives PCs an opportunity to start in a harsh but not entirely impossible situation if they are good and start in one of the western kingdoms.
But if a DM wanted to bring back all of the Lords of Sin he would only need to rewind the date back to the year 8160, when all of the Lords were alive.