Yeah, I've been kind of shotgun blasting with posts about Bloodborne, but I have been making pretty steady progress over the last few days, so oh well.
However, after a kind of surprising one-shot of the Shadows of Yharnam, I fought the... seven? additional enemies to get to Rom, the Vacuous Spider.
Much like Amelia, Rom's kind of a barrier boss, and defeating her will move the world over to its new state. And given that she's important, I'm not exactly concerned about the fact that I'm not totally facerolling her.
The thing that's weird about Rom though is that she's... it's?... really easy for about 50% of her health. She drops her little spiderling adds (oddly, she doesn't really look like a spider at all) and kind of chills there while you work on them. These guys can hit somewhat hard, but it is a boss fight after all (though the Hunter NPC in Byrgenwerth is kind of a boss of his/her own, though I managed to cheese that fight by spamming Auger of Ebriertas.)
However, once face two starts and the comets start raining down, that's when things get tricky. It's really hard to see where they're coming from and when they're going to come, so I often get her to phase two (her first teleportation) and then die pretty promptly.
The thing that's throwing me is that her own health goes down pretty quick. I've tried the "kill all the adds" strategy and the "just focus her" strategy, and both work ok for that first phase, but those comets really take me down.
Still, I suspect this is one of those fights where once you figure out how to dodge that one really devastating attack, it becomes a cakewalk.
EDIT: Still working on it. I've burned some Twin Bloodstone Shards to upgrade my Tonitrus and get the lightning damage on Rom.
I definitely think this boss is going to take some iterative learning, much like Amelia. One thing I suspect could help is making sure to hold off on unloading all my stamina into attacking her in case she starts to teleport, which is when I want to get a lot of hits in (I think I actually managed to interrupt her teleport at one point by doing a ton of damage, though she just did it again when she recovered.)
I summoned Henrik for an attempt, and while he certainly made clearing the little spiders quicker, somehow a second group of spiders spawned nearby after she teleported - I don't know if this is a counter to seeking help or just a glitch, but I'm going to hold off on using up my Insight.
I think it's really just going to be a question of finding a way to clear the adds in phases two and three without getting destroyed by comets and then knowing when to back off for her big AoE burst, and I should be able to get her down. But I suspect it will take several attempts to get the rhythm right.