I was just running around on the server I have with my friends, and I saw something pop up with a health bar called "You didn't see anything". It was only there for a split second, and I couldn't react quick enough and get a screenshot. The main mods we have are Advent of Ascension 3 (Nevermine), Openblocks, MrCrayfish furniture, Tinkers Construct and Davincis Vessels. Does anyone know what this health bar might be referring to? Thanks in advance.