This quest will be unlocked only if during the main quest The Night of the Long Fangs you selected option A - you decided to meet with Orianna in her mansion in Beauclair (M4,16) and ask her about Unseen Elder. The woman won't share the information for free - first you will have to complete this quest. During it you must check what is happening in the orphanage outside the city (M2,17).
Investigating the orphanage
After reaching La Compassion Orphanage (M2,17) you will learn that a massacre occurred there. Geralt and Orianna will find a boy who survived. During the meeting you can use Axii to calm down the boy and ask him about the monster that attacked the orphanage.
Activate Witcher Senses once the conversation is over and start searching the orphanage. Inside the building you will find bodies of two dead children. On the courtyard before the building you will find traits of the monster, blood marks on the wall and a few new bodies. You must look for trail until Geralt determines that a vampire-like creature called garkain is responsible for killings. Open the journal and read the entry in the bestiary about the creature.
Finding garkain's hideout
Follow the wagon tracks using your Witcher Senses
Keep using Witcher Senses and find the tracks of the wagon at the main road leading from the orphanage. Since the tracks are clearly visible, you can follow them on your horse - this will allow you to save some time. Keep traveling until you reach the damaged wagon.
Examine the cart using your Witcher senses
Get off the horse and examine the dead horse. Then walk towards the wagon and check it in order to find a corpse.
Find the garkain's hideout using your Witcher Senses
Keep using the Witcher Senses - the pulsing circles will lead Geralt to the nest of the monster you seek. You will find Garkain after reaching the bridge - the creature will hang under it.
Killing the Alpha Garkain
Alpha Garkain is considered as a boss (his health bar is shown at the top of the screen), so you should prepare yourself well before fighting this monster. Similarly as when facing other vampire creatures, use vampire oil and prepare the Black Blood potion. In addition to that, you can equip Moon Dust or Samum bombs and some medicaments against poison. Set Quen or Igni as active Witcher Sign. Quen will help you in avoiding damage if you don't manage to dodge one of the attacks. Igni will allow you to successfully burn the garkain and make him vulnerable to further attacks.
Try spending some time on learning garkain's attacks. In addition to fast attacks with upper limbs the beast has two unique abilities. The first one is a very high and fast jump after which it attacks with its crawls when returning to the ground. You can avoid this attack by jumping to the side at right time. The second unique ability is creating shockwave that can stun Geralt and make him a vulnerable target. If you see that the monster is preparing to use that ability, try moving away from it as fast as possible. Thanks to that the wave won't reach you.
Look for opening to attack after each of his unsuccessful attacks. It might be even easier if you use Igni sign - if garkain is set on fire, he becomes vulnerable for a moment and you can attack him with no fear. Try making it impossible for the boss to hit you because he can poison Geralt. If that happens, you must quickly use antidote or at least some stronger healing items.
Collect a trophy from the garkain
Walk towards the corpse of the monster after defeating it. Search the corpse and obtain the Garkain Trophy.
Return to Orianna
Now you can go back to the orphanage. Once you reach there, you will learn that Orianna is a vampire. No matter how you behave, you can't provoke her to combat. Inform her about eliminating the monster responsible for the massacre. The woman will share with you information about the place where you must look for the Unseen Elder and she will give you Magic Key.
Tell the birds you're ready to meet Regis
Go to the marked tree, interact with it and confirm that you want to meet with Regis. During the conversation the vampire will try convincing Geralt to go search for Syanna - as shown on the above picture. It's the last chance to decide whether you want to continue going towards the bad ending or to start moving towards the medium or good ending.
- If you select first dialogue option, Geralt will ignore Regis' suggestion and he will look for the lair of the Unseen Elder. This decision will guarantee access to the bad ending after completing the last main quest. If you selected this option, then you will start a new main quest - What Lies Unseen.
- If you select second dialogue option, Geralt will listen to Regis and will decide to find where Syanna is held. In this case the main quest The Night of the Long Fangs will be resumed and you will be able to try unlocking the medium or good ending of the game. If you selected this option, then go to the walkthrough for The Night of the Long Fangs quest (Examining the child room section).