Just bash their heads in and pinch the blood samples straight off their corpses. A fairly straightforward endeavour, really.
Collect yourself a sample of Dark Elf’s, Orc’s, High Elf’s, Woof Elf’s, and Falmer’s blood.
On your way out you’ll have a cheeky catch-up with Hermaeus Mora himself.
Septimus needs the blood of several Dwemer-like species’ to open this big Dwemer lockbox of his.
Return to old Septimus at Septimus Signus Outpost.
Now pick up that Runed Lexicon and maybe that Elder Scroll too.
Hit the second button from the left a couple times.
Hit the third button (from the left) till button two lights up.
Place the Blank Lexicon in the middle.
Once you’ve hit your objective marker, you’ll be faced with a room basically containing a centuries old Rubix cube. Try not to get your head kicked in by Dwemer robots while you’re at it.
Traverse the cavernous depths of Blackreach.
Hit it with your Attunement Sphere, baby.
Descend the deep dark depths of Alfhand ruins, till you hit that Dwarven mechanism in Alfthand Cathedral.
Shuffle on over to the nearest set of half-buried Dwemer ruins (Alfthand is just South-West of wintery Winterhold).
Take on his generous offering of an Attunement Sphere and Blank Lexicon.
Speak with Septimus Signus – sat, being a general lunatic, alone at his self-titled Outpost in a cave North of Winterhold.
You should be Level 15 before starting on this one! It also runs concurrently with the main questline – as in you’ll probably end up doing this one whichever way the wind blows. Skyrim: Obtaining The Oghma Infinium Artefact from Daedric Prince, Hermaeus Mora
Wear those bloodstained Ebony garbs and wear them proud.
Pick up that poor champion's sweet Ebony mail.
Bludgeon Boethiah’s champion’s brains out.
Mosey on over to Knifepoint Ridge, West of Falkreath.
Bludgeon the Boethiah cultists’ brains out.
Instruct them to Use the Pillar of Sacrifice.
Stare deep into the eyes of your good friend for the very last time, smiling warmly.
Bring one of your trusty companions to the shrine of Boethiah.
Chat up that Priestess of Boethiah watching two cultists batter each other.
They could have just called it a shrine but ok), East of Windhelm stables and up in the mountainside.
Hit up the Sacellum of Boethiah (Sacelleum is Roman for shrine don’tcha know.
Just bear in mind that you’ve gotta be Level 30 to get it on with Boethiah. Skyrim Boethiah's Calling Walkthrough - Oblivion Walker Ebony Mail - Daedric Artifact # 12
Enter that starry Star, and defeat the tortured soul within.
You’ll get either Azura’s Star (the fixed version) or the big Black Star respectively.
Hand over Azura’s Star to either big Aranea (from the quest’s beginning) or old Nelacar at the inn.
Steal his stuff along with that broken Azura’s Star. See that skeleton in his throne? Poor sod.
Soon you’ll hit a bunch of steps somewhere in the Deluge.
Keep on keeping on until you hit that barred door near the end.
Follow the Dungeon’s twisting corridors.
Strike out for Illinata’s keep (which be West of Riverwood).
After intimidating, bribing, or persuading Nelacar for info (Speech matters…Speech or money or muscle) He’ll let you in on the last known location of his mentor – who was playing around with Azura’s Star (Azura’s Daedric artefact).
He’ll point you to Old Nelacar (also in the inn).
Strike up a cheeky convo with Dagur at the Frozen Hearth inn.
Get yourself to the pretty standout Shrine of Azura – South of Winterhold.
Skyrim: Daedric Artifacts - Azura's Star & Black Star ("The Black Star" quest)