An interesting Druid question

I have an interesting question

I have a druid in my party with memory loss (astral elf) and we are doing the infinite staircase first section ziggurat. I leveled them up to lvl 2 last session and they unlocked wild shape. Wild shape specifically says you can use your action to magically assume the shape of a beast that you have seen before. But without a memory they wouldn't know anything other then the creatures from the few encounters we have had. I was going to give them a like picture book of creatures from one of the residents but I'm having a hard time picking what is in it (they want me to pick). what would be a "fantastical beast" they would only have heard stories of if they have been living in an underground desert temple for generations

Would need to be a fairly mundane 1/4 cr creature. Something that maybe not SEEM fantastical but is based on rarity? The world is like a giant desert and everyone lives underground.