See the reason I say Seath is because his first encounter is unwinnable. you cannot beat him, so going in you will lose the souls you have unless you know the fight and use a ring of sacrifice. This is pretty much the same type of fight, go in grab your item, die and then go from there just that you can easily win this without the item or follow an npc quest and have the npc beat him.
Bed of Chaos is a terrible design and there is a reason the phases do not respawn. So through the series there has always been those silly moments I just think others far outweigh this one.
The Dragon boss when you enter Archdragon Peak