Svarog, the Last Dragonborn, plans to wage a third Great War against the Thalmor. To do so, he feels the people of Skyrim need to be united first. In the previous two wars, the Thalmor launched their attack in conjunction with their declaration, taking the people by surprise and giving them little time to organize and prepare. So, Svarog asked the party to visit the Jarls of each hold and ensure that they were willing and ready to launch an attack on Thalmor bases of operation within Skyrim.
The party came to find that the majority of the Jarls were more than willing and ready, but three locations posed a problem. Sibbi Black-Briar, Jarl of The Rift, did not care about Svarog, or a war with the Elves. He made demands of favor and possibly a payment to be involved. Siddgeir, Jarl of Falkreath, did not care for Svarog and cared more for money and political position and arrested the party upon the mention of Svarog's name. Figmund, Jarl of Markarth, was willing, but had an ever-growing concern with the Forsworn and could not devote his troops to supporting Svarog when the Forsworn could conduct a repeat of the Markarth Incident during the First Great War.
The party endeavored on an escapade against the Forsworn and dealt with several key installations in the Reach. After defeating the Forsworn at Dead Crone's Rock, and chasing off Melka, the soldiers of Markarth could readily lend aide to Svarog. With only two holds in opposition, Svarog then led his attack on Sky Haven Temple, there confronting Elenwen and Umbalmo while others in his service attacked the Thalmor Embassy, the city of Riften, and the city of Falkreath. With two Jarls torn from their thrones, and replacements found, and the Thalmor in Skyrim completely uprooted, Skyrim was thus free of the Thalmor's control and the Third Great War would begin.