Third Wasteland-Eidel War

The Wastelands unite under the banner of a quartet of royal ghouls.
Eidel, despite having made many technological and structural advances, isn't well-equipped to handle this. Eideli combat doctrine simply isn't built to handle something like a greater ghoul, entities against which a spindle literally can't exert enough force to meaningfully damage. Even the experimental heavy spindle units could do little here (though they provided more meaningful resistance outside of formation-based warfare).
Eideli historians often say that while the Second war taught the empire structure, the Third taught them the importance of spontaneity. Only combat alchemists and arcahe could even hope to drive off the ghouls, often incurring heavy losses in the process. Many a combat alchemist makes their name here, several elevating themselves to nobility- though admittedly, only a handful of such 'houses' make it through the war.
The Wasteland forces push deep into the empire, pillaging their way through an entire province. They never quite make it to Eidel itself, stopped by a titanic blood construct.
With the bulk of their forces gone, one general dead and another crippled, the Wastelanders are in a poor position. Almost immediately afterwards, a third general simply vanishes. Some call him a deserter, while others theorize that he'd been assassinated: witnesses of Fetterer's Pass paint a horrifying image of Eidel's true capabilities.
The remaining forces consolidate, and end up making a fighting retreat. The fourth combat-capable general goes down stalling for the army to escape, liquefied by copious amounts of arcahe venom and sealed in a jar for research. The final, crippled royal hides in the shadows and bides her time.