The Elder Scrolls V: Skyrim

This achievement is for collecting 15 of the Daedric Artifacts in the game which is the max amount you can get in the base game. The Skeleton Key would make 16, but it does not count towards this achievement. The list of the 15 quests you'll need to go through and what artifacts are obtainable through them is below. I go through all of these more in depth in my video guide.

1. Azura's Star/The Black Star
2. Dawnbreaker
3. Ebony Blade
4. Ebony Mail
5. Mace of Molag Bal
6. Masque of Clavicus
7. Mehrunes' Razor
8. Ogham Infinium
9. Ring of Namira
10. Sanguine Rose
11. Savior's Hide/Ring of Hircine
12. Skull of Corruption
13. Spellbreaker
14. Volendrung
15. Wabbajack

For this achievement you'll need to get married. The process is pretty simple, but there are a lot of options and it can get complicated trying to marry some people. I also created a video guide going over all of this here.

1. First you'll need to head over to Riften to the Temple of Mara or the Bee and Barb to talk to the priest Maramal. You can ask him about marriage and then buy an Amulet of Mara from him.

2. The second step is to obtain an Amulet of Mara which you can do by buying it from Maramal, completing "The Book of Love" side quest for Dinya Balu in the temple of Riften, going to the lovers tent on the beach north of Dawnstar, or by finding one on a corpse or in a chest.

3. While wearing the Amulet you'll need to talk to an NPC that likes you, and is a potential marriage partner. The list of all available NPCs is below. To make them like you just do whatever quest or quest line is associated to them. Some are as easy as just paying to have them as a follower, and some you'll have to go through a whole quest line. Once you talk to them and you both say that you're interested in marriage you can move on to the last step.

4. You can then go back to Maramal in Riften and let him know that you're ready to get married. Then the next day you can go back in to attend your wedding and get married.

Females:

Aela the Huntress
Aeri
Anwen
Avrusa Sarethi
Borgakh the Steel Heart
Brelyna Maryon
Camilla Valerius
Dravynea the Stoneweaver
Ghorza gra-Bagol
Gilfre
Hilund
Iona
Jenassa
Jordis the Sword-Maiden
Lydia
Mjoll the Lioness
Morwen
Muiri
Njada Stonearm
Orla
Rayya
Ria
Senna
Shahvee
Sylgja
Taarie
Temba Wide-Arm
Uthgerd the Unbroken
Viola Giordano
Ysolda

Males:

Ainethach
Angrenor Once-Honored
Argis the Bulwark
Athis
Balimund
Belrand
Benor
Calder
Cosnach
Derkeethus
Farkas
Filnjar
Gat gro-Shargakh
Ghorbash the Iron Hand
Gregor
Marcurio
Halbarn Iron-Fur
Moth gro-Bagol
Octieve San
Omluag
Odfel
Onmund
Pavo Attius
Perth
Quintus Navale
Revyn Sadri
Roggi Knot-Beard
Romlyn Dreth
Scouts-Many-Marshes
Sondas Drenim
Sorex Vinius
Stenvar
Torvar
Vilkas
Vorstag
Wilhelm

How to be a Vampire or a Werewolf

Before we start, it's possible to becoming a Werewolf if you were a Vampire and the other way around. But you won't be able to becoming a Werewolf again, because Aela the Huntress won't do it twice.
It's advised to make a save before choosing.

Vampire

By characters : Harkon and Serana

• If you follow the main quest from DLC Dawnguard, you can be bitten by Harkon or Serena after you rescue her and take her back to Castle Volkihar.

By disease : Sanguinare Vampiris

• If you already are a werewolf, or an Argonian or a Bosmeri, you can't contract this infection because of immunity to diseases.
• You have 10% chances to contract it by being victim of Vampiric Drain Spell or weapons using by vampires.
• Or you can go to Redwater Den to drink from the Redwater spring to contract it easily.

By console commands

• DLC only : player.addspell xx0037E9

Werewolf

By the Companions questline

• Just do the Companions quests in Whiterun and you will be one of them during the quest The Silver Hand

Talk to Aela the Huntress

• If you are a vampire, you can ask her to make you a werewolf again

Perks

First of all, I advise you to lower the difficulty so you can kill quickly and easily

Vampire

• You can transform multiples times per day, whenever you want, but be careful with the sun !
• You can only gain perk by a power attack bite (Melee Mode, on the ground, but with a % and on humanoid with low health) or a Drain Life spell (Blood Magic mode, flying, left hand)
• Each new perk requires a total of 156 feeding to complete the entire tree
• Take in priority Unearthly Will (Blood Magic cost 33% less)
• Take the Night Cloak perk last because bats will steal your kill
• Leave your follower during your farm

Werewolf

• You can only tranform one time per day
• If you finish the quest Ill Met by Moonlight, and don't kill Sinding (the Werewolf), you will obtain the Ring of Hircine (Daedric artifact) that grants unlimited werewolf transformations, so go for it !
• You can only gain perk by consuming the heart of a corpse as a Werewolf.
• Each new perk requires a total of 164 feeding to complete the entire tree
• Take in priority Savage Feeding (you can eat from dead creatures)
• Leave your follower during your farm
• When you go back to normal, all of your equipement has been removed so don't forget to put it back when you are done

Place to farm :

• if you make a save before, you can go on a rampage in every cities.
• if you don't want, you can quick travel to an imperial or stromcloak camp, bandit camp (Helgen ...), caves (Tolvadld's Cave ...)
• for Werewolf : you don't have to kill while in Werewolf form, you just need to feed from corpses. So if you are more comfortable with your own equipement, kill all living things and then transform to eat.