Regarding the spells:

Purple Eyes: What can it do exactly? I'm getting a sort of Batman investigation mode from the Arkham series vibe from it but I could be wrong.

I'm not sure about the curses they all seem easily broken you can freeze the blood inside the human body that is alive. You can also boil them from the inside out. It's touch activated but that means the second you touch an enemy servant, or master they're pretty fucked unless I'm misunderstanding the concept.

Also doesn't Mana Dowsing flat out negate the attempt to hide from your master?