Did you know that the Crimson Bat needs to be fed more than 4200 people a YEAR? Its maintenance feeding is on average 100 people per week.
Now this likely has a big impact on where the Bat can be located. Ideally you would want to place the Bat in an area with a relatively high population density, where it could be fed prisoners and slaves – people who do not need much work to be rounded up. This would mean putting the Bat in the Lunar Heartlands, West Reaches, Saird, Lakrene, or around Furthest. But of course, you can’t keep the Bat there long – these are areas loyal to the Lunar Empire, but rounding up the local population is going to test that!
Places like Dragon Pass are a problem as their population density is low, they have plenty of places to hide, etc. Although the Bat cultists are experts at finding such people, this takes time and runs the risk that the Bat might go hungry. Maybe send it out to a rebellious area and let it eat its fill until the rebels flee. Then you can send the Bat back to more secure areas.
If the bat gets hungry, the Bat cult loses control as it feeds on ANYONE.
When the Bat is nearby, the local rulers round up whatever undesirables they can and send them to the Bat Feeders.
The Bat is worth the effort. It is a mobile Glowspot, absorbs all magic cast upon it, devours spirits, and demoralises enemies merely by being present. The Lunar Empire is not victorious because its soldiers are particularly that awesome – they aren’t. The Lunar Empire is victorious because it has things like the Lunar College of Magic, the Crater Makers, etc. And because of the Bat.