So, the story until then, my horse got killed by Froststalkers out of nowhere by those, I lost a diamond horse armor and a saddle (couldn't even figure out where or why my horse died), but I gave these things the benefit of the doubt and thought it was my horse's fault for wandering into the ice. Shortly after, I lost ANOTHER diamond horse armor and saddle the exact same way by just being minimally close from a cold biome - by that point I was starting to figure out that mob is BS. For the third time, I was fine at home with my horse, stopped looking at the horse for 2 minutes and, despite being almost 100 blocks away from the small amount of ice that there was at the top of the mountain near my house, and I get the message that my horse got killed AGAIN. I didn't want to lose a third set of horse armor and saddle, so I looked around to see if I could find my horse's items. I killed about 10 Froststalkers, realized there were at least still 20 of them, seemingly endlessly spawning constantly, then I went into the mod's config and disabled their spawns in frustration. Just 5 minutes of wandering around, killing several of them and getting slowly but surely destroyed by them, physically and morally, they went down the mountain with me and mass invaded and raided my base and everywhere around, to a point where eating food, running away and blocking up, I didn't even have enough time to run a /kill command to finally forfeit and kill these freaks with a command, then I died and lost my XP. This is the screenshot showing that moment:

EVERYTHING about the Froststalkers is just ridiculously unfair. They have lots of HP, lots of damage in different attacks, they are decently fast, spawn frequently in a ridiculous amount, are almost impossible to predict or dodge, have ridiculously far attack range, don't seem to take fall damage, and their ranged attack is also almost impossible to dodge - you just have to facetank this mob, there's no strategy, except you'll be facetanking an endless horse. The cherry on top of the cake is that they decimate any pet you want to have. Absolutely no fun is allowed if you're even rendering a cold biome at max render distance - and they're one of the most useless mobs in this mod, as their drops are basically useless.
In the current state, these aberrations should be disabled by default, as almost every single thing about them is overtuned and they have no use other than ruining your experience with the game. Please fix if possible, will definitely be keeping them disabled but now it's a bit late.

... Hell on earth
I ran "/kill @e[type=alexsmobs:froststalker]" and it killed 550 entities... Suddently I'm pretty sure this is an overspawning glitch on top of everything

EDIT: This comment (not the main issue) was solved in the last update (at least according to the patch notes), and can be safely ignored as fixed

I'll admit this one is more of a personal b*tthurt than a real issue but I must say Skelewags are pretty unbalanced/broken too - their head is almost entirely outside the hitbox, they deal damage from outside the head that's outside the hitbox, they can freely chase you on dry land and hit you up to a dozen blocks away from water, and they significantly outswim a boat. It's so discouraging to explore the ocean with this nonsense. That's the second mob I'm having to disable, wow