On the subject of the We I've been thinking about some alternative possibilities for communication in the event of the Talking Beast spell failing. Some of my current ideas are:
1. Writing. Just use a notepad and a pencil.
2. A speaking voice dog. A dog (or other animal) with The Talking Beast who can listen to what the We is saying and repeating it in another language. However this probably won't work, it's been noted that The Talking Beast can only be used to make an animal speak a language that the caster knows, which is why the We can only speak Reikspiel and not Khazalid, the Wizard who made the enchantment only knew Riekspiel. It might be possible to work around this by giving the We an item enchanted with Master's Voice to compel the speaking voice dog to say certain things even if it doesn't directly understand the We. This is however complicated and probably inferior to the other solutions.
3. Illusion. Give the We an item enchanted with Illusion that can be used to make any speech sounds they need. Problem, would require either a way to interface with the We's mind or have manual controls which would be very complicated given how many possible phonemes there are, would probably need something like a stenographers keyboard attached to it.
4. Human interpreters. Create a body/sign language that allows for the We to communicate words and concepts solely through body movement and have a staff of human (or humanoid) librarians who are trained to interpret that language and act as translators to others who don't know the We's nonverbal language. Would be a good way of including Verenan librarians into KAU, long-term they'll become inferior to the immortal We but having a justification for keeping them around even if they are otherwise redundant would make the Verenans happier since they get to feel included.
5. Birbs. There's a spell in the Celestial spellbook called Birdspeak which allows you to talk to birds. Unlike The Talking Beast it is not cast on an animal, it's cast on your self hopefully meaning it doesn't rely on the caster's understanding of a language to work and instead simply makes it so the statement that the target can speak to birds is axiomatically true, in the same way Invisibility doesn't bend light around you or make you transparent, it makes you invisible because magic says so and reality knows better than to pick a fight with magic. An additional casting of The Talking Beast could allow any bird to act as a translator for the We but an even simpler solution is to skip that part and use birds who already have the natural ability to talk as translators. The most well known talking birds are parrots but there are others such as mynas, starlings, mockingbirds, lyrebirds, and plenty of corvids including crows, ravens, magpies, jays, jackdaws, and a familiar friend, choughs. A library filled with talking birds does have a nice fantasy vibe in my opinion and this option is probably my favorite. If we want the Verenans to still feel useful they can be subordinate librarians to the We even if they are completely redundant as actual librarians and their only actual use would be to deliver books to the reading rooms for those too arachnophobic to enter the library itself.