All normal weapons have been translated, but I don't know where the legendary weapon description file is.

Hey there,

The legendary/unique weapon descriptions are from line 483 in the lang file:
https://github.com/Sweenus/SimplySwords/blob/Architectury/common/src/main/resources/assets/simplyswords/lang/en_us.json

Just want to double check, did you find everything you were looking for?