Like I said though, even if it does work, I don't think it would be effective enough on its own. Look at what it does to vampires in Buffy for instance, it doesn't kill them for sure, just causes serious injuries. I don't expect it to be much different for Angra.
There's enough of Hollow Ataxia translated for me to have gleaned that much, since I certainly can't read Japanese. Most of the main storyline's been translated. More than enough of it to see how Avenger fights. And while Avenger is indeed a seperate entity from the corrupted grail itself, he does give an idea of what Angra Manyu's abilities would be like as a Servant. In fact, this is
exactly what Avenger is. Like, literally.
In terms of Angra Manyu as a separate entity here, technically she shouldn't be able to manifest physical entities outside her host. Well, aside from familiars like the dog monsters and Sakura's shadows anyway.
We saw what happened with Sakura and Irisviel- Angra never formed a separate form from either of them, merely possessed them and carried out its will through
them, with its personality being shaped by the one it possesses (Avenger is similar- while how much is the actual young man that was sacrificed and how much is Shirou is debatable, there is some of Shirou's influence there. Also, there's a similar argument with how much was Sakura and how much was just her being corrupted by evil, but let's not start that here). So really, by what we've seen Angra Manyu do in canon, it shouldn't be able to form any physical form outside of Toshi
period, whether it be a castle or the form of a girl.
Yet again, though, Elf's decision here. Ultimately, in an RP such as this one, it's the GM's call on what's acceptable and what's not. ...I'm going to repeat this over and over until it burns into some skulls.