what this really means:
The ochain is sentient, like the relic weapons, and it likes to sing. It's also probably a bit of a masochist, so each time it blocks a hit, it squeals with joy in a sing-songy manner. The reason ochain's blocks return mp is because the shield is singing ballads about how much it loves to get smacked. Personally, I'm imagining a voice something like Tim Curry's, but a little higher in pitch, and metallicky.