I think that Kalamar is flexible enough to handle this. Here are some ideas:
1. The Evil Kalamaran Emperor (it is your destiny, Luke!): The Emperor of the Kalamaran Empire can be portrayed as a ruthless and power hungry tyrant with every ounce his will bent on world domination. He has already conquered, subjugated, and enslaved the great dwarven capital of Karasta and roots out the remaining rebel forces from their caves as we speak. He also pushes a tributary through a war of expansion and a brutal trade embargo, trying to reclaim territories lost to the Empire hundreds of years ago. Word is that in the siege of Karasta he employed the aid of evil humanoids to complete his vision of conquest. What dark forces is he in league with? To further complicate matters, the player characters have met a most remarkable individual who claims to be the heir to the long lost line of kings, a decendent of Theodorus himself, and he claims that he can obtain the item he needs to prove it...with a little assistance of course. His historical lineage, if what he says is true, holds the hearts of the people and gives him the ability to challenge the throne of the great Emperor himself, bringing rebellion home to the front porch of the Emperor even at the height of his despotic expansion abroad. The fate of the world now balances on the edge of a sword...
2. The Secret Network of the Blue Salamander: An organization with agents planted in governments throughout the world, it is the largest secular group in the world. Their mysterious leadership (which some speculate may consist of illithids who murdered the former leaders and secretly took over control of the organization) is also bent on world domination, but there are perhaps some other, secret hidden goals beyond this.
3. The Re-unified Hobgoblin Empire: The hobgoblins have been suffering from an economic collapse, poor health conditions, and long protracted military campaigns without resolution. Perhaps all it would take to unite the northern and southern empires would be a leader with enough charisma and vision to feed upon the fears, insecurities, and misery of the hobgoblin peoples. With a new and sudden vision of power, the economy goes through a sudden explosion of growth, fuelling a tremendous military buildup unlike any seen before on Tellene. Claiming Allies from various sources, including Pel Brolenon, the Theocracy of Slen, and the city state of Saaniema (which had sudden renewed interest in their own long past dreams of conquest), the tremendous military engine of the hobgoblins finally rolls into action, and the blitzkrieg begins as the squabbling and politically disintegrating kingdom of Zazahni is quickly toppled and made into a vassal state, further fuelling the economy and war engine of the hobgoblins. The Brandobians, in their typical manner, have declared neutrality in the war, so the only force that has any chance of stopping the powerful axis is the glorious and mighty Kalamaran Empire, which even now seeks allies in Zoa, Geanavue, it's former enemies in the Young Kingdoms, and the remaining free peoples of Svimohzia. The face of Tellene will never be the same.
4. Pel Brolenon: First established as a utopian community, the release of a long captive evil god corrupted the ideals of the people of the fledgling nation. It has now grown to become the center of the world slave trade and the sight of the masts of it's fast, efficient, and unsinkable ships is enough to strike deadly fear into the heart of even the boldest of captains. What happened to the dark god who was released so long ago? Most likely he returned to his eternal abode on another plane, but just perhaps he lurks still, in an ancient crypt deep beneath the dread, labrynthine city of Dowond-Brandel, as his terrible priests do his bidding, spreading slavery and oppression across the face of Tellene.
5. Slen: Three miles high and above the clouds, defiling the upper slopes of crooked peak of Mount Shakota like a black cancer, lies Kako-gyr, wherein resides Grand Theocrat Toth Senkan, the terrible ruler of the Theocracy of Slen. At times, the wind carries the voices of the tormented from Kako-gyr and across the mountain peaks.
6. From the Great Rift in the Elos Desert, strange artifacts have been discovered of an ancient civilization. As the party goes in hopes of unearthing long lost treasures they discover that the cliff dwellings dug high into the cliff walls, unknown to previous explorers, are only the external outlets of a vast underground network. In their explorations, the players unknowingly unleash a terrible evil, which pours from the dark of the rift and threatens to cover the world in darkness. Perhaps the ancient libraries of Dishijy hold the key to stopping this evil before it is too late.
These are all ideas inspired by the campaign setting. Only #3 and #6 have a bit of liberal expansion on the setting material, but they still have material from the book at their core. The other four ideas are all pretty much straight from the book.
By the way, the Emperor of Kalamar is left ambiguous enough that you can play him in many different ways, thus #1 and #3 both referring to him in quite a different light depending on the needs of the campaign. It's nice and flexible that way.
