There are not one, but two store pages for the "Caster of Magic" DLC / variant / patch!

Caster of Magic for Windows
Master of Magic - Caster of Magic

Both pages incorrectly claim that you need the base game. In reality, the base game runs as a launcher that provides four buttons (image here)
Original
Original with community patch
Original with Caster of Magic patch
An ad for the new 2022 remake

I have the "classic" product and oddly enough, the Master of Magic - Caster of Magic DLC product page shows "in library".

These two store pages that sell a "Caster of Magic" that seems to require the base game should not exist because the base game already includes that variant.

EDIT: I see the reason for two web pages. One CoM is dosbox (just like the base game) and the other CoM is native Windoes (but says it requires the dosbox base game). Still, the base game already includes CoM. so at least one of these product pages has no reason to exist.

EDIT 2: It seems that "Caster of Magic for Windows" isn't just a native Windows port, but also includes new features that aren't in the dosbox version? it would be a bit more obvious if called CoM II instead of "for Windows". Still, the doxbox CoM is redundant.

Honestly, everything about MoM in recent times seems redundant.

Well, not everything in fact, the drake178's unofficial patch 1.60 is amazing.

But everything else, Seravy's CoM and 'CoM for Windows' abominations, and especially fresh stupid 'remaster', is not just redundant but revulsive.

I just got into this series recently, so I am still happy with the original game and all it has to offer.

But I've heard a lot of good things about Caster of Magic and the significant AI update in it. It is probably true that the new AI makes some tactics and playstyles that you can use in the old game, practically unusable to win over the AI, but I don't think that is a big problem, since the old game with all its greatness and problems is still available to play for all who have it.

I've never understood the mentality with some players that you can only use one version of a game. If it is an old game, like in this case, there are no problems using one for one type of a game, and then using another for a different type of game. In this case the original Master of Magic offers you a lot more freedom to make the kind of empire you want, while the Caster of Magic games gives veterans of the series the possibility to go up against a challenging AI.

For Heroes of Might and Magic 3, I really like the HOTA mod. But I still play a lot of games with the original balance provided by New World Computing, because I like that one a lot too.

For Heroes of Might and Magic 2, there is a project I haven't tried yet called fHeroes2 that I am very happy exists, because it should be able to give a lot of new life to the game with a totally new AI and mod capabilities. But I will always keep around an installation of the original Heroes of Might and Magic 2 regardless, because a new engine with a totally new AI will never feel completely like the original game.

As for Caster of Magic, which I haven't tried yet, the only thing I don't like about it is the replacement of graphics in the Windows version. The new mountains look like something out of a Super Mario game. They do not fit at all in the Master of Magic world. Hopefully the developer replaces these with the old ones, or at least gives players the option to use them again. I think there were also some problems with playing in full-screen in that game, but hopefully those have been fixed by now.