This creature is never seen alive. The only trace of its existence is the stuffed or artificial cuckoo bird which is part of a clock in the Gervaisius Estate, seen in Casing the Joint and Masks.
Story[]
I could tell you where it is, but that would spoil all the fun...
This section contains spoilers! Read on your own peril.
The cuckoo is required to adjust the clock near to the haunted library on the second floor. Once set to the correct time, the clock opens a secret passage to the third floor.