In addition to regular enemies found throughout the non-instanced maps in MapleStory 2, there are regularly spawning World Bosses and Elite Monsters.
World Bosses are boss monsters who spawn hourly at various maps. They are significantly challenging, and require multiple people to defeat before the boss despawns.
There are currently 18 World Bosses in MapleStory 2.
Elites monsters are mini-bosses who spawn every five minutes throughout the world. They are relatively easy to defeat alone, but teaming up to defeat them will expedite the battle. Some may even drop cosmetic outfits reminiscent of the boss, like the [Placeholder] eyewear.
There are currently 21 Elite Monsters found in the field in MapleStory 2.
Additionally, there are 5 Elite Monsters who must be accessed via sub-maps.