See the Category:Guest Monsters for a full listing of these enemies.
Guest Monsters are monsters found only in Act Five on Nightmare and Hell difficulties. They were added to the game in v1.10, when that patch broke up the non-variety of monsters found in Act Five in v1.09 and earlier versions. Guest Monsters are more powerful versions of monsters seen earlier in the game, sometimes with different names. Guest Monsters often have some palette shifts, and a few have new skills or abilities as well.
For ease of navigation, this Wiki lists Guest Monsters on the same pages as the normal types of monsters, but sets them apart in the tables to make clear which are which.
Act Five
The addition of Guest monsters in v1.10 played havoc with the Act Five-only expansion monsters. Many subtypes no longer appear at all, and others spawn as though they were guest monsters, appearing only on Nightmare and Hell difficulties, but unlike all of the Act 1-4 monsters now appearing in act five, the original Expansion monsters have unchanged stats. In other words, they're regular monsters who happen to not ever spawn on Normal difficulty. They are listed as Guest Monsters on their pages though, for the sake of consistency.