Contract: Deadly Delights - Novigrad
Quest Giver: Harborside Notice Board
Other Requirements: N/A
This quest begins by inspecting the Notice Board in the Harborside portion of Novigrad. Upon speaking to the guard who issued the contract your quest will update and send you to a medic by the water in the north-central part of town. He'll update your quest again and this time send you to the crime scene which is in the central portion of Novigrad.
When you arrive follow the hoof prints that you find in the crime scene through an alleyway and to a brothel by the name of Crippled Kate's. In the alley that dead ends near the entrance to the brothel you'll also find a perfume bottle which will update your quest and give you a scent to follow.
There are two ways for you to do the quest now, you can follow the scent to your target or go inside and talk to the brothel owner and reach your target that way. If you talk to the brothel owner you'll have to use Axii to get the information you want, demanding it won't work.
If you follow the scent, you'll have to run through the town a bit until you find someone who smells like the perfume at the bottom of some stairs, speaking to him will update your quest. Now, in order to get inside of the building with the succubus you'll have to go inside of one of the buildings connected to this one and up to the second floor. Use my screen shot below for guidance.
As much as you may not want to, kill the Succubus. The mutagen from the succubus' are extremely rare, this is one of two in the entire game (not including expansions). You'll need it for Alchemy if you wish to make every potion possible. If you let her go, you'll still get the Succubus Trophy, you'll just miss out on the mutagen.
Whatever your decision is return to the contract issuer when you're done to receive your reward.
Tip: Sparing Salma's life gives you credit towards helping monsters in Contract: Skellige's Most Wanted.