"By rights, the Flat of Elaedh should be Common land. But what I saw come from the heart of Merellien did not just look like an army... it looked like the end of the world. So long as our lords in Emblem retain a shred of sense, we would do well to never step foot past Fort Verdane."
The Unholy Siege of Fort Verdane was the instigating event that lead to the signing a true declaration of Common Unification. Months prior having its borders officially established, the southern Common Leage regiment continued its expansion into Elthys. It passed by historical borderlands down the Flat of Elaedh in an attempt to treatise with the historic house of Merellien, hoping to add Elthys to the League by coercion rather than force.
Before their regiment could approach the capital City of Merellien, however, they were set upon by a horde of Undead, composed of numbers greater than any standing army in the world. Facing down a slowly-moving tide of bone and flesh, the southern army was forced to retreat. As they made their way back up the Flat, their teleporters reported their situation to the Common bastion of Emblem. Wizards and Artificers from the capital moved quickly, setting up a series of magical gates with a strong fort behind it, designed to withstand a ground siege. Strategically, the fort was built to occupy the space between the Farmouth Bight and the Jawstone Divide, and was constructed just in time before it was set upon by the horde.
The newly-named Fort Verdane stood strong against these forces of darkness for nearly a calendar month, with supply lines being shipped from other nearby territories of Commona. With much of the undead tide decimated and the Fort still intact, Merellien's remaining forces diverted east through the Sea of Trees, attempting to circumvent its gates via a mountain pass. The undead abandoned their siege and attempted to enter Commona through the Howling Hollowland. No trace of the enemy was ever seen again; most speculate that they were consumed by an even deadlier enemy in the forest depths.
The Unholy Siege was considered a landmark battle in Common history and a testament to the military might of the united League. However, since the building of the Fort, the alliance between Commona and Elthys remained uneasy. While no formal battles were declared after the Siege, whispers remained that Merellien harbored an intense grudge against their northern neighbors.