The Beast of the Sewers is one of The Witcher's ten trophy quests - the third available, and the only one which is automatically initiated in the course of the main plot (it is not technically assigned by Vincent Meis, but he does require that the cockatrice be slain (and looted) to advance the primary quest, Prison Break).
Walkthrough[]
After killing the Beast and escorting Shani to Vizima's walls, Geralt is betrayed by Mikul, who hands the witcher over to the City Guard. All is not lost, though, as Captain Vincent Meis provides a way to win passage out of prison: by defeating a greater cockatrice which roams the sewers. This seems an ideal option for our hero... But first he is pitted against a fellow prisoner ('Muscleman') in a fistfight to determine who makes the first attempt.
Having settled that issue one way or another, Geralt descends into the sewers, where he meets Siegfried of Denesle, a knight of the Order of the Flaming Rose. He can either accept the knight's offer to team up against the cockatrice, or go it alone. This decision will have repercussions during Chapter II.
The 'Cockatrice Lair' is marked on Geralt's map of the sewers even before you find it; approaching it from either direction will trigger a brief cut scene, followed immediately by combat. Addan Aenye is recommended. Also the Igni spell is very effective.
Notes[]
- Search the remains of the beast for not only the trophy head, but also the Maal'kad sephirot.
- It is not strictly necessary to complete this quest to be freed from the dungeon; that quest is Prison Break, which leads to this quest and must be completed to advance the plot. However, there is no way out of the sewers until the cockatrice has been killed, and it seems a shame to waste the opportunity for extra orens. (As with all trophy quests, this one is all about cashing in the trophy head, which can be done at almost any time.)
Phases[]
The Cockatrice[]
I killed the cockatrice and took its head as proof. I should see Vincent now. I need to deliver proof of having killed the cockatrice to Vincent.
A New Employer[]
- This phase only occurs if the quest is unfinished when Chapter II ends
Vincent no longer holds the key to the coffer. I should see the Royal Huntsman about my reward.
Proof[]
I delivered proof of having killed the cockatrice and received 400 orens. I received my payment for the trophy. (400 
+ 3000 XP)