Yes, I realize I play this damn game too much! But I love it...=)
Anyway, I was fighting the Four Kings after getting the Lordvessel (I wanted to see what Kaathe would say if you answered "No" to his question/choice), After three of the Kings were killed, the Fourth one, who was spawned had an issue. I figured out the Abyss is nothing but a big square (or rectangle) play area, and where the Fourth one spawned, was in one of the corners...making him effectively stuck! Sadly, he was too far out to hit with a weapon, so I 'eased his pain' with a Crystal spear or two, before I beat them again.
This is actually the THIRD major error in regards to bosses. This current playthrough, while co-oping with someone on Sif, he actually backflipped on the wall, near the entrance, and could not get down. As my host had mainly combustion, and other close-range weapons, he resorted to using arrows, while I zapped a few magic spears and gave him a couple Demon Titanites for making me laugh at the error (very nice dude, whoever he was...)
I went to solo the Butterfly soon after, but on the way, an invader came, but didn't attack. I was frustrated, so had Beatrice zap the dude away, and continued on to the boss...however, the Butterfly went straight from the tower, to the ground, well out of range of both magic and arrows, eventually 'killing' itself...=/
Anyway, bunch of weird things happening this time!
Edit...I now am in love with the Priscilla Dagger...at +5 I cut up some invader very fast, and the high bleed rate finished him off. =p Reminds me of my original Bandit Knife (that got 'promoted' to a Great Lord Sword of Gywn...or whatever it is called)