Just a little note about your post, we're not commanding armies here.
This is a team-based attack on the Dead Haunts raiding zone as detailed in the main Ragnarok thread, boss mechanics and mobs included. It's a progressive thing with loot drops that necessitates teamwork.
How about a Korgon prince spurned from the throne and who tried to win his country back, finding the journey harder than expected. Backed into a corner, he finds clues about a runeblade somewhere in the mountains and uses it out of desperation. Its power is too much for him to handle, and he falls to the whispers of Ebonfrost - the cursed lynchpin of the Desecrated.
Korgon becomes a desolate wasteland, a sacrifice to the Overlord of the Damned.
Interesting piece of Skellbrieg lore, the Desecrated are not weapons of the Infernal Phalanx. It was created as a weapon against the Phalanx by the first Overlord of the Damned, Sergei Karnov. But the power of the artifact he used to start the Desecrated plague proved too strong for him to handle. His soul was bartered among the various demon lords of Fargate until he became one of the Seats of Chaos based on his sins in life and the sacrifices he made to attain such power.
Lore-wise, there has been an Overlord of the Damned. Emperor Doom killed him and took Ebonfrost back to Elysia.
Winter War in the OP is all about the attack on Korgon, which opened the floodgates between the Frigid South and Midland. Ever since then, the Desecrated (Scourge) has run rampant, paving the way for an invasion from the Worldscar by the Infernal Phalanx.
Resistance from Skellbrieg's natives has been hard, however.
It might just take another Overlord of the Damned to break them.