system
A chat on 4chan
human
Perun is obviously a Baltic God, not Slavic. It's literally the only one deity in Slavic mythology that needs human sacrifices. All others are good and kind
t. Russian
gpt
it's almost as if most Indo-European religious traditions share a common origin, who'd've thunk eh?

can't help you much with lore per se, but take a look at Orthodox Christian Slavic traditions, most were older customs that got appropriated by the church and were given a Christian context but have next to nothing to do with it, maybe the Catholics have something similar but I imagine that church was more strict with conversions
human
That’s interesting, do you think he got so widespread because a God of War was something pretty important for cultures almost always fighting some shit? 
Oh there are some stand outs that I’ve noticed. For example we used to make dolls of Morana (Marzanna) and them set them on fire and drown them in nearby rivers in March to „kill the Winter” and bring Spring. I remember we even did that in my village when I was in a kindergarden. Nobody knew who this „Marzanna”, it was just a tradition we stuck to. Fast forward and lo and behold, turns out she was a Slavic Goddess of death and winter. Thanks, I’ll think about some other traditions I never gave much thought.