A game of two gimmicks: it takes place largely in total darkness, and the mechanics centre around wordplay. Among its many problems is that players may take quite a while to fully notice either of these.
Like earlier wordplay games (Nord and Bert Couldn't Make Head Or Tail Of It, Ad Verbum) Erebus mostly eschews coherent plot and builds itself around word puzzles. The tone is wacky Zorkian, and the writing's main strength lies in mildly amusing silliness. The setting is the main divergence from this: islands in a dark subterranean lake, with an atmosphere not unlike like the game's namesake Hunter, in Darkness. This, combined with the opening sequence, make Erebus feel rather like two games that aren't quite on speaking terms; a Zorkian wordplay game set in a wacky hell, and a moodily surreal game about darkness and silence.
The core gameplay is about constructing short words from letters that you've found. The most annoying thing about Erebus is that using a letter consumes it; a replacement appears where it was originally found, and this entails a great deal of unnecessary trudging around the map. The second most annoying thing is that some of its puzzle solutions, particularly towards the end, feel quite arbitrary; this exacerbates the first problem, because the only real way of working the solution out is to try making lots of different words. Erebus shoots itself in the foot by saddling its fun central mechanic with tedious makework.