Culling of the Hounds
The Culling, as it's called, was the ill-fated plan by the Hounds of Balthazar to eliminate the liches. With their forces split between the two fronts, they failed to slay either lich, though they wounded Rotscale, permanently grounding the beast. This has left the Hounds a fraction of their previous number, with them having to give up several fortifications, and focus on what they could hold.