The Witcher Bestiary - Zeugl
Zeugl Occurrence: Zeugls live in filth, in sewers or waste dumps; they should be disposed of while they are young and small a fully grown zeugl is a formidable adversary, even for a witcher.

Immunity: Practically immune to sword blows, regardless of whether the sword is steel or silver.

Susceptibility: To kill a zeugl one has to remove its tentacles first.

Tactics: They shower their opponents with numerous tentacle hits.

Alchemy: Zeugl venom.

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.