Tanith is one of the many questline in Elden Ring and is one of the best in my opinion and it is also important to do it. Also you become the invader so do it!!!!
The questline starts in the top of the map in Volcano Manor when you join Volcano Manor. After speaking to her she will give you the drawing room key that you can use to open locked doors in the Manor. In one of the rooms there is a letter on the table that shows you where to go to eliminate some guy.
The first person you assassinate is Old Knight Istvan located in front the colosseum in Limgrave. When defeated he will drop a Rune arc and a Furlcalling Finger Remedy. After that return to Volcano Manor but first speak to Bernhal and then Tanith, that will unlock Bernhal as a shop guy. Talking to Tanith will give you the sorcery "Magma Shot" and a new target.
Pick up the second letter and go to the location that the red mark tells you to. Your next opponent is Rileigh the Idle and is located to the south of the Bridge of Iniquity that is the bridge that you use to enter Mount Gelmir. Defeating him will give you Crepus's vial and some Black-Key Bolts. Go back to tanith and she will give you a Serpintine Blade
Thats a bad picture I know
Before you carry on with the third assassination you speak to Bernhal. He will give you a letter to kill two other guys, Vargram the Raging Wolf and Errant Sorcerer Wilhelm that you can find near the Divine Bridge in Altus Plateau. When you invade them Bernhal will join the battle so it will be a 2v2 and defeating them will give you Raging Wolf Helm, Raging Wolf Armor, Raging Wolf Gauntlets and Raging Wolf Greaves.
This assassination will be the last and looks the best in my opinion. The guy you are going to kill is Juno Hoslow, Knight of Blood and you can find him near the Shack of the Lofty in Mountaintops of the Giants. Defeating him will reward you with Hoslow's Petal Whip, Hoslow's Helm, Hoslow's Armor, Hoslow's Gauntlets and Hoswlow's Greaves. Once defeating him go back to Volcano Manor and speak to Tanith to earn the talisman Taker's Cameo. She will say if you want to go to their "Lord" which is Rykard and if you want to meet him. In Volcano manor there is a teleporter that brings you to Rykard but this route is wat more fun.
Juna Hoslow art link
Agreeing to Tanith will teleport you to the Lord's Chamber. In there walk forward to the fog gate and you will be meeted by Rykard lord of Blasphemy (The easiest boss in Elden Ring). In front of you will be a Serpent-Hunter sword. The Serpent-Hunter sword is like the sword you use the defeat The Storm King in Demon Souls and is a good weapon overall, just spam him to death.
If you go back into the boss room where you fight Rykard and Tanith will just be sitting there so attack her and she will dissapear. Wait a couple of seconds and you will be invaded by Tanith's Bodygaurd. Defeating him will give you Aspects of the Crucible: Breath incantation, but unfortunately you will not be given its armor set.
