Bombernauts is a game developed by Tyler Glaiel (Eyebrow Interactive) and released into early access on 31 Jul 2015.
The sigil was added in an update on 12 Sep 2015.
There is a level called Sigil. It is basically the image of the sigil made up from the different blocks of terrain.
Players on the level are given custom titles:
There is an Awesomness setting in the options menu that takes a text input (used for other easter eggs as well). Filling it with
CRIT will make the semi-transparent puzzle piece appear on screen while on the Sigil map.
Discovery process notes
The discovery of the game by GameDetectives was tipped off by the developer retweeting an article about the ARG.