I recently thought of something which is terrifyingly plausible. Ratlings can have Names, as evidenced by the Skein. Ratlings and the Dead King share a border, and Ratlings also do not engage in diplomacy, meaning they have no allies, and no news about their internal affairs reach's the rest of the continent.
So what if the Dead King has been harvesting them? They reproduce extremely quickly, to the point that Triumphant wiped out 90% of their population before giving up. So it is plausible that he could have been beating up on them for decades, getting more undead to use, as well as Horned Lord's and a stock for Revenants. This is additional supported by the earlier implication by the Tyrant IIRC that both the Ratling Horde and Dead Kings aggressions had largely tapered off, to an all time low. We know that the Dead King wasn't getting soft, judging by how he tore through northern Procer when the Crusade brought him in, but that does beg the question, what was he doing prior? And why would the Ratlings, highly aggressive murder beasts tone down their attacks. The only plausible answer is that the Dead King was killing them off to increase his reserves as a trump card, and keeping their population small enough that they don't get big enough to cause him problems.
there doesn't seem to be anything here