The unicorn cannot be conquered by the hunters and can only be caught by a pure virgin. This signifies that Christ, mightier than all heavenly powers, came down into the womb of the holy virgin to accept humanity. (The Latin texts, and with them the translations into the vernacular languages, go into more detail here, as in other sections of the interpretation, with citations of further biblical passages. The essential further features are as follows: That the unicorn has only one horn means that Christ and the Father are one. The fact that it is small signifies the humility of Christ in his human value. That it resembles a goat means that Christ took the form of us sinful humans).
The idea of the BIBLIOTHECA BESTIARIUM is based on the medieval animal poems of the Physilogus, in which animals were given human characteristics. These tales were mostly inspired by the Christian doctrine of salvation and have survived to this day in figures of the unicorn or the griffin.
I asked the machine about the Bestiary, and this is what it gave me......