>>535476818
As the other anon said, it's literally just Black Grail without the HP drain but with a restriction to only work when a Berserker is holding it. So it's just objectively slightly better on Berserkers, useless otherwise.

>>535477078
Has some fringe usecases. For example, Saber Artoria can use this to refund more from overcharge, allowing her to loop with this despite not being able to with a normal Black Grail. It's use is very specific to servants that have specific effects on Overcharge, in other words. Aesc is also another good example.

>>535476972
I want to see this clearly so much. That front facing intense stare from Rikyu is so beautiful.