Quick idea here, one that the devs can actually implement fairly easily.
Would it be so hard to add a 'bestiary' on the main menu?
Pretty much, let us view the monster cards+stats for immortals we've personally killed, as if were making a 'deck' of monsters-standard immortals, bosses, and monster immortals (hydras, dragons etc). And maybe later, creep creatures, if we ever add those.
I know there's a counter every time we down a boss, so it shouldn't be too hard to link those cards to the main menu in some way.
If we ever get around to adding more+improved bosses or different types of immortals (or even creeps+immortal creeps) that's going to be a lot of information on our enemies that would be really useful to have. It'd be useful to have right now.
If I see some Orcs barrelling down on a mana pool, for example, I pretty much have to dredge my memory to try and remember what sort of bosses are going to pop out. If I am about to lose a monster base, is it really fair if I have to guess what sort of strange abilities they have until they literally pop out and attack?
It wouldn't impact the game much (you'd still get that 'ohshi' factor when first meeting something new, before you add them to your 'deck', they would be a total surprise to you), but afterwards it'd be really helpful to have them all listed down neatly. Instead of hoping someone makes a wiki or something, and maybe you can find it, and hope it's still updated.
I was thinking, you guys will probably be adding a bunch of righteous+corrupted cards to the lists at some point anyway, so why not add this along with it?