So I haven't seen any posts for this yet and it didn't seem like the most obvious commendation to grab so for those who are looking to find out how you get this commendation. So this commendation will be unlockable after the silver blade encounter and before the Siren Queen fight, in between these locations you will find this room: https://gyazo.com/1a0362969db6af010a4d2192bc05c366 . The door the arrow points to will be closed, optionally it might require the eternal chest of sorrows to open but I can not confirm and if anyone is willing to test without bringing the chest and it opens let us know! Inside that room will be 5 etchings on the walls that look like this: https://gyazo.com/e4e631c289cb62ddf6afcb423af98648 , once you inspect all 5 wall etchings the commendation will unlock.

Again I haven't seen anyone post about this commendation yet so I felt like starting one once I found the room so if there has been a post prior to this one my bad.

Quickedit: Gyazo links don't seem to just show the picture and don't work with picture links so you'll have to click on them to see the pictures.