Monsters! another question about what-was-it-then

Short answer: Fayre beast (or fearie).

In Araby is a kynde of beast that some men call Garsantes, that is a fayre beast (The voiage and trauaile of Syr Iohn Maundeville, knight; 1568) (cited for example in The Giraffe in History and Art, Berthold Laufer, 1928).

Longer answer: beast seemed obvious from the start, and etymonline marks it as “early 13th century”, which fits. I spent some time looking for the right adjective, even though I had spent some time earlier this morning in writing a somewhat comprehensive etymology of fairy and related words. It then dawned on me, and Google Books confirmed at least one use (but they don't have many books that old, so it's hard to gather statistics).

Fifel, þyrs, and eoten are good Old English words that typically mean 'giant' (or 'demon' in the case of þyrs) but also mean 'monster' in a generic sense. It looks like none of these words particularly survived into modern English. Etymonline has mod. E. ettin for the last, but that's not exactly conversational. Beowulf has fifelcynn 'monster-kind'.

Wight has the sense of 'monster', especially of supernatural origin, in addition to the broader meaning 'animal'.

Besides wight there are other creature-words which may be modified with fay or other such words as appropriate for the time period (unsælige, eadily, eldritch, etc.), especially deer and beast in any of their various spellings.