Quote Originally Posted by Picker View Post
Wtf is mare, is it an app that makes your chocobo a horse?
Mare Synchronos is a Dalamud plugin that syncs cosmetic mods between game clients. You have to opt in to who you share with but that way you see people's changes in game rather than through screenshots. You'll often see people put Mare Lamentorum in their search information to signal that they're using this third party tool.