Had a question, low fantasy is restricted to what limit?
It's not like there some Universal Fantasy Scale that we can say "BattleMaster only uses things that rank 15 or lower" on, but I can try and give some guidelines.
Wizards exist, but are incredibly rare, and only findable by adventurers. Having one as a PC or in any meaningful way associated with a PC is out of the question. Our characters performing magic is pretty much exclusively limited to the scrolls we can get from adventurers.
Monsters and undead exist, and are not particularly specified in form, so it's not unreasonable to RP as having fought skeletal warriors, shambling zombies, trolls, and maybe even dragons (particularly in the past when incredibly powerful monster groups roamed Dwilight, or in the Fourth Invasion).
Gods are ambiguous. They can have no game-mechanic effects on the game, so it's reasonable to state that they can have no effects on RP that cannot be explained away as a charlatan's trickery or the delusions of a single character. However, it's also reasonable to state that our characters can converse with the Gods they believe in. (After all, anything they claim to have heard from their Gods certainly falls into the "can be explained away as a delusion" category.)
Unique items are not magical: they are simply items with a storied history, like Joyeuse, the sword of Charlemagne, or the Crown Jewels of England, such that simply possessing them would show that you are an impressive and noteworthy person. (The minor exception is items that improve one of your skills; however, that is the limit of magic that unique items can possess.)
You shouldn't read too deeply into the names of items adventurers can find. Just because your character
believes that it's a griffon's egg doesn't mean it really is. After all, you're only a commoner.
It's important to remember that many mythical creatures were
known to exist in medieval times, and even afterwards. For instance, Johann Jakob Scheuchzer, a respected scientist in Zurich who had written treatises on paleontology and biology, also wrote an account of the various types of dragons that were
known to live in the Alps—in
1723.