Now, answer me this: is it worth sacrificing (or at least weakening) your Pit Lords for a mere ten demons?

In this particular example, it's definitely not worth it, as it's simply foolish..., but :)

So, tell me, what would be your reason for taking Pit Lords into a Utopia? To turn their flesh into ten demons? Is that right? Is that right?

That's incorrect. :)
You yourself said that this game is about logic, right? Right. So, let's just consider a situation where Pit Lords are simply indispensable – it's not that difficult. Let's say we have three Utopias on the map (let's consider an online game). The main strength of the kingdom's army is, of course, with the main hero, but he's already on his way to the enemy. However, due to certain parameters, there's a risk of defeat... So, we create a chain of heroes to avoid wasting precious time, and the situation is such that the secondary hero's army is too weak without Pit Lords to capture the Utopia. Do we take them? We do. Even if we lose 5-6 of them, we gain valuable parameters, and as a result, we achieve victory. Is that possible? It is. :p

That's it, I'm tired of arguing. :)

Yeah, we've certainly started quite a discussion... :D – it's probably time to wrap it up. :)