[quote=@Hinsek]
<Snipped quote by Crimson Raven>

Achilles is still invincible to it right? I don't think it's a divine beasts of anything. But even so you're also right in that Achilles can't kill the beast either and people with more vanilla servants like Masamune literally can't do anything
[/quote]

I have no idea how Achillie's immortality could face up. It is part of the time before the Age of Man, so it would be targeted. And he, unlike that, has a legitiment and exploitable weakness-- his heel. Even more so, since he is Lancer, not Rider.