Ezekiel and Alvis

Ezekiel and Alvis were discovered in one of the Polish forests, where some hunters reported an 'Unusual Rabbit' terrorozing the area. Upon its burrow being discovered, the animal patrol discovred hundreds of lost artefacts and meaningful historical books safely preserved underground. The word of its existence spread even further when a well-known historian of mythology and legends - Julian Kowalski - had 'adopted' it instead of letting the authorities take care of it.

Why did Julian adopt Ezekiel? And was it true that they were the last of their kind, now destined to live on only in legends and child stories? Pray tell, who was the spirit - the Kaja - that was following them everywhere?