Some monsters might become special when spawning, these special monstera are called "Gloomies". They get additional abilities and are tougher than their normal version. They also give more xp and have a higher chance of dropping items.
Dropped items from gloomies also have a chance to be magic.
They can be of different types. The kind of gloomy can be seen on the color of their aura.
Green = Flash (more speed)
Red = Scorching (Have fire abitlies and fire resistance)
Yellow = Electro (Have shock abilities and shock resistance)
Blue = Frosted (Have cold abilities and cold resistance)
Purple = Infected (Have poison abilities and poison resistance)