Batak… so those things could even break through Ivos battle formations while having volleys of long armour/shield piercing spears launched into them? (Pilum, if the Ivos share that characteristic with the Romans, the heavier Pila were weighted down with a lead ball so that they would hit a shield and bend, making the shield useless. This worked for the lighter pila, but the lead made it that much more effective at piercing. Needless to say, you get hit by one of those at close range and…). If so, then I suppose that our good Praetor would have countered them with tactics similar to how the Romans defeated Parthian Cataprachts, keep them on the field as long as possible, particularly in the sun, and force them to tire out, then butcher them. Or open the formation lines and surround them.

The Batak knights were pretty few in number (about 1000 total in the whole last war, out of a Nameless army of over a hundred thousand) so though they were devastating, their overall effect on things was more limited.
The reason they were such a small part of the Nameless army is unclear to people in Vellastrom, as a lack of cavalry was a weakness in the Nameless armies in general.
Some have theorised that this might be because of difficulties in involved in keeping large numbers of non-nameless creatures alive in the West.
There are rumours of groups of Nameless raiders mounted on a new kind of Batak. These steeds are said to be hairless, with greenish-grey skin and bleed the same foul green blood as the Nameless. So far, no evidence has been found to back up these outlandish claims.

Another factor to consider is that Batak knights were not deployed against every type of troops available, or against every commander, but those that did face them in large numbers invariably found them over an over whelming force.

Now, how would you deal Batack knights? Me, I'd go with one of two things. Lots of prepared Ivos Legionaries (if they are how I suspect), or the Golta. Do Golta have landmines? Because if they do then I'm not sure I see them losing a pitched battle easily. And, really, just mass Golta rifle fire into the charging Batack knights. They are almost too big to miss, and too slow to close fast enough. They might even get in a good couple of volleys.

I'm wondering, do the nameless generally armour their Batacks? I could see that being a problem with overheating and tiring them out quickly. But if they don't armour them… Sure, big nasty critters and all, but pila would go straight into them. Even with armour it is dangerous how much damage a good weighted pilum would do. Then again, I'm not entirely sure. This is the world of Harkovast, where sling stones thrown by focused overgrown lizards can go straight through wolf people! (tongue in cheek! I swear!)

Also, does this mean that Sir Muir took out about 0.3-4% of the Nameless cavalry from the first war? In one sitting? Next to a church? And add to that the fact that most of the nameless pursuing him croaked on the way? I've got a newfound respect for Muir. Unless those weren't “The” Batack knights, just a bunch of dudes riding Batacks, but that doesn't seem like the case.

Now, I've noticed that the Nameless don't need to eat, or sleep, etc… so that means the “undead/nameless” Batacks might not tire either. That would be a serious, serious, problem. Then again, perhaps they don't exactly reproduce all that easily. The zombie things don't entirely look… healthy. If that is the case then the numbers would still be limited…

That also begs another question. How do nameless reproduce their numbers? Do they actually reproduce? Or are there pockets of little mouse/rat people still around used as breeders in the West?

Possibly that is why The King In The West is trying to conquer the rest of the world, for breeding stock to replace those lost.

And I think and excellent way of dealing with batak cavalry would be caltrops. 4 nails welded together so there will always be one pointing upwards. Then you make a couple of thousands of them and spread them across the battlefield.

Calthrops and lands mines are great but they require you knowing where the enemy is goin to attack from and having plenty of time to prepare before they do (without them sending scouts and noticing what you are up to!)

How do Nameless reproduce?
Well sometimes when a daddy Nameless and a mommy nameless love each otehr very much they…alright that was a joke. The details of where Nameless come from will be revealed in time (probably quite a long time!)

Additional- Yes those were actual Batak knights, though the figure of a thousand is the total deployed in the last war. How many are currently in the KITW's armies is unknown. But Sir Muir always kills noticiable percentages of his enemies. Cause he is awesome like that.