So if you go back to the Asylum later in the game (which necessitates you being hyper aware of your surrounding and getting a little creative) and enter your former cell, you'll find a Peculiar Doll. This doll allows you to enter the Painted World of Ariamis, a place where those with no place in the real world are exiled.
At the end of this nightmarish (at least for me) area you encounter Priscilla, a being who looks like half god/half dragon, who asks that you leave the Painted World. That's right, she doesn't even want to fight you. But this is Dark Souls, and we're kind of a jerk.
As soon as you attack her she turns invisible and the only way to find her is to look for her footprints in the snow and once you've hit her she remains visible. From there, she's pretty simple to dodge, just watch out for the bleed buildup from her super cool scythe. You can also cut off her tail for a Dagger.
This fight isn't the best, but the invisibility gimmick is neat. It would've been cooler if she'd gone invisible more often, though. The lore about the gods being afraid of her Lifehunt ability is what makes her lore so interesting.
The popular theory is that her parents are none other than Seath the Scaleless and Gwynevere, Princess of Sunlight. Gross.
38) Crystal Sage
Dark Souls III
At the end of the Road of Sacrifices you are met with what appears to be a plague doctor-like entity wearing a familiar large hat and casting sorceries at you. This phase is pretty straightforward, dodge the magic and wail on the Sage. He will teleport around the area, cast some crystal spikes from the ground (that I guess are supposed to hurt you?) and once you get health down enough, he'll bring in multiple copies of himself to throw you off.
This part requires that you keep an eye out for the real one (he casts purple magic) but simultaneously avoiding the attacks of the copies. They go down in one hit, but their spells'll take you out so fast it isn't even funny.
You also fight another one at the Grand Archives. There's some lore evidence tying these guys to Big Hat Logan from the first game, and it appears they became spiritual guides to the Lothric scholars. The one you fight as a boss apparently allied himself with the Undead Legion, hence the location you fight him.
This is one of the best designed bosses in my opinion, and while the arena is kind of plain it's still pretty cool. He's not too hard, but not too easy either.
37) Mytha, the Baneful Queen
Dark Souls II
Remember the Covetous Demon and how he engorged himself to win the affections of a queen? That was Mytha, who ignored him and desired only her betrothed, the Old Iron King. Unfortunately, he fell in love with another, driving Mytha to desperate measures. She then proceeded to POISON herself in an effort to make herself more beautiful! What the heck?
Anyway, all that poison turned her into the gorgon-like headless monster we face at the end of Earthen Peak.
Before you even think about facing her, do yourself and burn the windmill. Doing so will remove the pool of poison in Mytha's lair, which would otherwise sap your health and raise hers. Once that's out of the way, it's just a matter of dodging her spear lunges and the magic she shoots from her head, which she holds in her hand. Sometimes she'll even throw it into the middle of the arena for it to do a magical explosion.
It's probably a good thing that she and the Covetous Demon didn't end up together! Can you imagine those therapy sessions?
36) Old Dragonslayer
Dark Souls II
I'll admit I was pretty dang excited to see Ornstein return for the second game, even if the fight itself is almost a literal copy/paste of the original. The main differences are that Smough is not present, and that the OD uses dark magic instead of lightning.
Situated off to the side of Heide's Tower of Flame is the Cathedral of Blue, where we encounter this doppelgänger. From Software must really like this guy (for good reason) because not only is he here, but he basically shows up in the third game as well.
I have no idea why he's there lore wise, but I'm not arguing.