So I finally beat the ugliest boss in Bloodborne. Ironically, while he's the ugliest, he's also one of the most sympathetic - he's the first of the church hunters (and given that Gehrman is The First Hunter, I guess that means the Hunters were originally independent of the church?) and thus has been really horribly mutated by the Curse of the Beast, resembling a mix of human, horse, and buer (who I think inspired the "Roving Mauler," which has been on a number of lists of "dumbest D&D monsters.") Ludwig is somewhat famous in-game, given the popular Ludwig's Holy Blade and mentions in a lot of item lore.
The fight itself is very challenging, and to be perfectly honest, I did grind some to get my Strength and Vitality a little higher to beat this guy. He's kind of two bosses back to back, even with different names (though the same health bar.)
Ludwig the Accursed is when his mind is in total beast mode. He attacks viciously and fast, and while you can't exactly get in close all the time, you can cripple his legs to slow him down and if you do enough damage to his head, you can get a visceral on it. A lot of his moves are tough to dodge, and he'll move both forward and backward with some attacks. The absolute worst is that he'll sometimes jump into the air and land on you, doing absurd, often one-shotting damage. I learned to dodge this by simply rolling constantly in a line until he landed.
I got lucky sometimes by backing him into a corner and getting a few hits on his head. I don't know if it's my weapon or just the frequency of his attacks, but I seemed to be getting a lot of regain healing.
Oh, also, fire will deal extra damage to him, so I recommend getting some Fire Paper or, if you're going Arcane, definitely plugging a fire gem into your weapon.
Phase two starts when you get him to 50%. There's a maybe ten-second cutscene that will play every time. His Holy Moonlight Sword will drop out of its scabbard and he'll begin to regain his human mind.
Phase two is a completely different fight from phase one. He's now on his hind legs and wields the sword. This thing hits very hard, and he can often combo you to just wipe you out if you aren't very good at dodging.
His sword is magical, and there are a few really nasty abilities to watch out for. At range, he'll sometimes do a horizontal slash that sends a wave of energy toward you, but you can dodge this without too much trouble - dodging to the side worked for me, even if it looked like I should have still gotten hit. Sometimes he'll do a diagonal slash followed by another one which is sort of the opposite diagonal. You'll want to dodge one way and then the other to avoid these.
Occasionally, he'll get ready to plunge his sword into the ground. This signals an AoE that is relatively easy to dodge back from.
The absolute worst thing he does in this phase is that he will (if I recall correctly) raise his sword up and begin to cast a massive energy wave in front of him. If you're in this, even if you dodge the first blast of it, the subsequent ones will kill you. I honestly think I just got lucky that I was close enough to him on my last attempt when he did this that I could dodge around behind him and get a bunch of nasty hits in instead of, you know, dying.
Being in melee range doesn't mean you're safe either. Not only does he have his magical AoE, but his sword slashes hit really hard, require very precise timing to dodge, and will combo you if you get hit once.
Overall, while I found this boss very, very difficult and even frustrating at times, I still think that it's good and memorable. The cutscene in the middle of the fight maybe goes on too long for a fight you're probably going to be doing many times, but the music that swells in phase two is very epic.
Anyway, having beaten him (and already wearing the Executioner set with the Golden Areo,) I actually got to talk to his severed head. He asked me if the Church Hunters were still the noble spartans he had envisioned, and I lied to him, saying yes. I figure this guy has it hard enough being the severed head of the most disgusting monster in a game full of disgusting monsters without knowing that everything he fought for just led to insanity and evil.
For talking to him, I got his Holy Moonlight Sword, which appears to have very good Arcane scaling. I haven't attacked the head, just in case, but I'll look up what happens if you do. I also got a new rune, but I honestly don't remember what it was.
So that's 1/5 in the DLC and I think 10/14 in the main game.