The Darkness is one of the new monsters that lurk the dungeons in Ergastulum. It is the "collector" of lost souls and deadly to the living and deceased.
Since I had already added "Good" ghosts in the game, it made sense to also add an "Evil" one. Good ghosts that roam the levels are helpful and have not been "collected" by The Darkness yet. Since they were ghosts, creating them with just particles was the challenge ahead.
The Particles System
As shown above, the idea for The Darkness was to use several layers of particle systems to create the monster. The base of the particle system is a sphere (the black fog) with an additional layer for the subtle lightning.
To give is more depth, 2 Point Lights that spin were added. However, I believe the most important part in creating a good particle system is using a good Texture Sheet Animation with it.
Finally, the particle system is vertex lit, and by using a temporary yellow point light, you can see how it would affect the fog in real time.
Testing It In The Game
The Final Monster
After I was happy with the results above, all it needed was additional polish which can be seen here.