I get that some people are saying that it's an easy event because it's "just bats." Yeah, they don't really do a whole lot of damage to you or your buildings, but they sure can destroy your livestock. I had just come back from a frost cave and was just setting things up in my base when the event was triggered. I didn't think much of it because I thought they wouldn't do too much, until I started hearing my boar dying. I went out to try and fight them but it was very difficult to hit them, since they have such tiny hitboxes and there were so many. They ended up killing my 20+ two star boar, and my only wolf. I had two boar inside the house in case of any raids that would do this, but they got through the cracks at the top of my walls. I wasn't expecting bats and didn't think they'd be able to get through, but they did.
Yeah, I could protect them by putting them in a safe house so that no flying mob can easily get to them, but I really don't want to do that; I wanted my boar to be free-range, and at my main base I have nearly a hundred boar, I don't know how I'm supposed to get them all into a building, let alone build a structure without risking a raid.
Source: https://www.reddit.com/r/valheim/comments/upafmr/you_stirred_the_cauldron_needs_to_be_nerfed/