I finished the DLC as a vampire. Is there any in-game rewards to continue helping the other vampires at the castle? I have the rings from one of the quests. Are there any more items to get? Up next they want me to kill an important person in Solitude. I really don't want to keep killing off NPCs if it's not necessary.

Thanks.

for the npc kill,just kill a guard.
also you can get special amulets that boost your vampire lord powers as well as the rings you already have.

Yes. You get amulets too.

You also supposedly get ancient vampire body parts to further extend the blood of the ancients effect 3 more days..its repeatable from what I hear.

If you are married you can get a radiant quest to turn your spouse into a Vampire as well.

The High Profile killings are Optional, to a degree. Anyone can die, and as long as you do it in Dawnguard Armor, then the High Profile part is optional. If you don't want to kill an NPC who is rather important to you, then just kill someone. You'll still pass the mission requirements, it just won't be perfect. Besides, there are at least five people in each major city that I really don't care for and have never gotten a Quest from so... I could do these quests for a bit before it put me into a "bind".

As far as the Rest of the Radiant Quests, I love the Better Allies quests. You get to go to a Hold Capital and turn an NPC into a Vampire. This has a two-fold benefit.

1) They love you for it the next time you visit them. 2) If you have a Vampire attack on the city, usually they're the ones who just destroy the attacking Master Vamps whilst fighting right next to the Guards. You're creating them as a source of influence and info gathering for the respective area, but they're an improvised defense against Vamp attacks. I've turned three people so far, and given each one of them Ebony Swords Smithed up to Legendary. The threat of losing NPC's goes down with every vamp I make.

There's the fetch quests like getting the petrified remains of ancient Vampires for use in the Blood Chalice. The effect of the Chalice in my games is up to seven days long now with 3 or 4 (can't remember exactly) pieces of Ancient Vampires retrieved for the Chalice. The buff from the Chalice gets pretty beefy, so it's worth stopping by every time you get close to having the buff run out. Plus these quests cure that itch for a good 'ole dungeon romp.

And then there's obviously the quests for the four Vampire Artifacts. The artifacts are very, very good at boosting your Vamp abilities, so I don't see how they couldn't be beneficial.

The radiant quests are very, very fun, and add a new twist to being a Vampire. Plus you actually feel like you're helping to make them stronger all of the time.

My favorite Radiant Quest though, has to be when I get asked to turn my Wife into a Vampire. There's nothing like being out adventuring for a couple of weeks and getting to come home to Muiri the Vampire!

Thanks for the replies guys and a special thanks to Uriel Nocturne for the detailed explanation.

I killed a guard in Riften to complete that killing quest the first time. I was a bit surprised that it would come up again. I was hoping for some sort of elevation to vampire ruler or something along those lines, kind of like the Thieves Guild. I am going to shoot for the other artifacts and ancient vamp parts.

Thanks again.

You're welcome.

Also you can improve blood of the Ancients

Here's one better. My female Dunmer Nightblade is married to Jenassa, and i turned her into a Vampire. Two sneaky vampire [censored]es, nasty. You can even RP that they lure unsuspecting men with the prospect of a threesome, then murder and devour him. Reminds me of the "Siren's Deception" quest in Oblivion.

Does the bloodstone chalice buff effect your Vampire Lord drain, or your human form Destruction magic drain...or both perhaps?

both.