Bad Blood Walkthrough
After talking to Lann, take him with you to Upper City and Find Savamelekh’s Lair.
Savamelekh’s Lair is at Southwest corner of Upper City, below Rapture of Rapture, you need to pass a portal to reach there.
Savamelekh is waiting there with some of his mongrel followers, if you let Wenduag live, she may betray you now, depends on your previous choices, whether she is in your team or not. (To prevent Wenduag from death, you need to side with her at the end of Shield Maze, and finish her personal quest in ACT III. Or, you side with Lann, and during Lann’s personal quest choose the [Evil] diplomacy option and pass the check, telling Wenduag that serving in the Crusade is a great honor, one that she’s not worthy of. If you do this, you’ll be able to spare her and she’ll run off, and you’ll be able to recruit her in ACT 5.)
If you fail to pass diplomacy checks, Lann will be teriffried by Savamelekh, give him debuff during the fight.
Defeat all the enemies, then talk to Lann.