Tanith Questline

Quest Step	Location (Click for Map Link)
When you first enter Volcano Manor speak with Tanith and join the family, she will give you the drawing-room key, make your way down the hallway and into the drawing-room to find a letter
This letter asks you to assassinate Old Knight Istvan, his invasion sign is found just North of the Warmaster’s Shack in front of the colosseum. After defeating Istvan return to Tanith and speak with her, then go back to the Drawing-Room to find another letter
Your next target is Rileigh the Idle in Altus Plateau, their invasion is found on the path to the shaded castle After defeating Rileigh return to Tanith and speak with her, then go back to the Drawing-Room to find another letter
This letter asks you to assassinate Juno Hoslow, their invasion sign can be found just outside the Shack of the Lofty After defeating Juno return to Tanith and speak with her, she will ask you if you would like to meet their lord, if you accept she will teleport you to RYkards boss arena.
Once you defeat Rykard return to the Manor and speak with Tanith, if you reload the area she will be gone
Tanith can now be found in Rykards boss arena, speak with her then attack her to obtain her armor set. If you do attack her you will be invaded by her bodyguard who drops Aspect of the Crucible: Breath