The zeugl inhabits sewers predominantly, feeds on sewage, and grows at an alarming rate. The beast is always hungry, so it reaches out with its tentacles for living creatures and tries to shove them into its huge maw filled with multiple rows of teeth. The zeugl is paralyzingly hideous, foul-smelling, and surprisingly strong for something resembling a rotten potato, so it usually manages to devour its opponent.
Geralt was hired to rid the sewers of a zeugl during his and Yennefer's stay in Aedd Gynvael. There is also a breed of zeugl mutated by Rissberg mages called parazeugl, which in turn is not at all dangerous and cleans the sewers.
In the game, the zeugl is one of the boss monsters. Geralt must face this ugly beast in the Vizima sewers during the Epilogue, and this time, the tentacles seem to have a mind of their own! Luckily our hero is not forced to face the beast alone.
"The zeugl is the best example of a monster that has grown accustomed to human settlements. The beast feeds on the waste and filth produced by the city, so it need not hunt or fight to survive. It simply grows and gradually becomes a danger to people. This shows how detrimental continued degradation of the natural environment can be in the long run. Therefore, I implore the reader: respect nature."
- Sewers in the Epilogue
- According to Geralt just before they enter the sewers, zeugls are hermaphrodites that do not need a mate to procreate. In a hilarious conversation with Siegfried, he intimates that "zeugls do not need a Mrs. Zeugl to make little zeugls. They do it with themselves." To which Siegfried responds "That's sick! ... unnatural even for beasts!" This exchange is a paraphrasing of an conversation between Herbolth and Geralt in the short story "A Shard of Ice".
- Geralt can still extract zeugl venom after the fight in the sewers even if he has no bestiary entry for Zeugl (in case you forgot to buy one of the two source books earlier.)
This huge monster inhabiting the sewers beneath Vizima looks like a medieval environmentalist's nightmare. It feeds on the garbage and carrion that slowly drift with the flow. The zeugl can grow to be enormous in size, and being a hermaphrodite, it reproduces easily. A fully grown specimen is a serious threat to humans and very difficult to kill.Only the top part of its body and tentacles ever surface above the sewage — and these are the most important elements of its design. The black on red sketches present the creature in all its glory. Sapkowski described it as a "hideous bulge" — and such is our zeugl. The concept artist provided it with a fish-like head and a few rows of sharp teeth suitable for grinding whatever reaches the monster's jaws. If the victim is not quite dead, the zeugl's tentacles feature spikes that allow the creature to pull its prey into its mouth.
"The debris exploded in an geyser of thick, stinking grease, clay pot fragments, rotting rags and pale shreds of pickled cabbage. From beneath it burst a huge bulbous body, resembling a rotten potato. It slapped the air with three tentacles and the stub of a fourth. (...) The body glided toward him, plowing through the debris like a barrel being rolled to market. He saw the tuber crack as it opened its wide maw full of large, razor-sharp teeth. He let the tentacles wind themselves around his waist, lift him from the stinking grease with a thwack, and drag him towards itself spiralling ever deeper into the debris (...) The tooth-lined jaws snapping wildly and angrily."
- In The Witcher 3: Wild Hunt, when Keira slightly recreates her favorite fairy tale, Cinderella, Geralt explains how it was based on a true story where Princess Cendrilla was eaten whole by a zeugl that hid in the palace pond, leaving behind one shoe.