I'm about to finish Dawnguard and I'm fighting Lord Harkon but I have no idea how to kill him. My weapons do little damage and he regenerates so much health so fast every time I hit him with a arrow with Auriel's Bow he's already gained the health back. I'm not a vampire because I joined Dawnguard and I had to cure my Vampirism because I had nobody to feed on. Also, when you join the Dawnguard later in the story Serana gives you the option to be a vampire or have her put part of your soul into a soul gem, I chose Vampire but eventually had to cure it. Is there any way to become a vampire again?

You attack him by doing damage, like with any other enemy. Use Auriel's Bow to break the energy barrier he puts up when he floats by the fountain. After that, use any weapon or spell you prefer.

You can become a VL again by talking to Serana after you kill Harkon.

Like I said he regenerates health so fast he pretty much counters all the damage I just dealt to him. I am only level 22. If my level is what is stopping me I'll be stuck here for hours on end....

Just attack him normally and use Auriel's bow when he recharges then after a couple of times he will stop recharging so just kill him normally. If you gave him the bow you can still kill him but it will take longer. I killed him in like 3 hits as a werewolf.

Lower the difficulty

I took him out with my Nord Warrior/ VL like he was a preschool bully. It was actually kind of anticlimactic.

are you using sunhallowed arrows? i went in with 30 of them and about 70ish skill and it took all of them to kill him, hes pretty tough

I got him guys thanks for the help! Soul Tear rips him apart. Took down almost half his health hitting him with that shout. All 3 words are recommended though.

I used slow down time shout using all three words, so I could use fire storm that brought his health down 50%, then it took 4 shots with incinerate, and he was down (This is on novice) so much for a epic battle.

I was very annoyed with this fight....
I ended up having to lower the difficulty after being in a fight with him for about half an hour, he didnt hit too hard I just couldn't do any damage to him (regen was too fast)

He was pretty easy for me. My 230 damage wielding Dragonbone Sword cut through him like butter. I used Auriel's Bow when he used the energy shield though. I thought it was a pretty cool fight, definitely different than any other battle in Skyrim.

Use Sunhallowed Arrows when he is using his Blood Magic Field: let's him regenerate his health an Magicka. Then chip away at him, Took me 20 minutes on Adept

Exploding Dwarven fire bolts with the enhanced Dwarven crossbow.

Killed on master with my dragonbone sword legendary with 29 fire 29 frost, shield bashing, then the auriels bow when he was very low on health and serana said to use it. At first I was trying just the auriel's bow, which was kind of a joke.

'Course I was level 81 too, with my awesome dead thrall dual wielding (legendary dragonbone axe sword, with dragonbone bow too) forsworn ravager. She pretty much obliterates stuff, though I guess her max level would be 34. She wears forsworn legendary, double enchanted for one hand and archery, where possible.

Great thing about her as a dead thrall is, if there is a place she won't go (like the stupid soul cairn...) I can off her then loot all her stuff. Later, if her body is gone, I simply tour forsaken camps again until I see another forsworn ravager female, already dual wielding. Then that one is my new dead thrall,
loot her and plop in my already legendary enchanted stuff (which forsworn, unlike other dead thralls, will wear even if it is not their own original gear.)

It was a cool fight and prolly one of my fave but still his attacks were pathetic.