Uncatchable Beasts

Brooding Tarantula (upper sceptre of god) and an animal from Tora's missions (dont remember the name) are not ticked off the beastiary list when captured. Einhar normally comes and takes them, but the next one you see has the "new" thingy next to its name and the beast does not show captured in beastiary.

Fix those things as they make completing the beastiary impossible atm without mentioning how frustrating it feels. Probably there are more buggy beasts in this category and im sure a quick search in the bug/feedback forums could help you.

Your storage for that type of beast is full and beasts won't be overwritten if the new one has a lesser rarity than all existing (aka a white beast won't overwrite any magic/rare/unique ones). Consequently the new capture is instantly discarded and you don't get the unlock. Maybe the second part will get changed/fixed at some point so that an unlock happens even though the beast is discarded, but for now you can simply make room.

Look in the beastiary book which storages are full and use a recipe at the blood altar to use up a few beasts. I'd recommend the "unid rare ..." recipes, since they don't require any special mod, just two rare beasts of certain categories, so you should be able to find a recipe that frees up the storage in question.

47/56 in storage