I will say, the part after beating Death in IV, is one of the coolest, most atmospheric moments I've ever experienced in any game. Walking down the corridor while the candles light up...you know exactly where you're going. Still get goosebumps to this day from that. Such a badass moment.
While I'm talking about IV, the invincibility potion is one of the stupidest game design choices. It serves absolutely no purpose in a Castlevania game and was clearly included 'just because'. Maybe the team thought since Sonic had one, Mario had one, etc that Simon should have an invinciblity item. But the thing is, in the locations they have it, it feels like such an afterthought -- there are really no enemies in the first level where you get it and they pose no threat. What's the point to it? How will this benefit me? There is none and it doesn't.
That's always bothered me since childhood. When I was younger, I got it because hey cool no skeletons gonna hurt me now, but then I grew up and realized the harsh truth, that it's a fucking stupid idea and a terrible design choice.