its a masonic symbol for the inside of the temples.
I saw a picture of owls engraved on the inside of a temple on a profile like this lookinf for it.
The word mass has never been used to my knowledge with masonry specifically. There is the gnostic mass with the oto. But a masonic mass i have never heard of that have you?
>mass
think that was a solitary satanist that made those pics nvm. There probibly is a masonic mass but its not gonna be on social media.