Monsters are hostile Mobs that will attack the player on sight (with a few exceptions), with no warning. They tend to drop useful Items, which means that despite their danger, they must eventually be sought out. Many Monsters have variants with different abilities and stronger attacking capability, such as the spider and the higher ranked spider warrior.
Monsters do not regenerate health over time, so you can for example strategize to attack Boss Monsters with intervals to stop and regenerate health for your own, muster allies to swarm it, eat or recover sanity, etc.
It is unclear if Mobs eventually despawn. Experiences detail that they do not, so, for example, if you flee from a hound attack and come back, they will still be there unless they wandered off to attack other creatures. The Deerclops, on the other hand, will disappear when Winter ends, without any trail or Items left behind.
Reign of Giants Monsters
|Hostile Monsters||Batilisk • Cave Spider • Clockwork Bishop • Clockwork Rook • Clockwork Knight • Dangling Depth Dweller • Depths Worm • Frog • Guardian Pig • Ghost • Shadow Creature • Hound (Red Hound • Blue Hound) • Killer Bee • Lureplant • MacTusk • Merm • Mosquito • Spider • Spider Warrior • Spitter • Tallbird • Tentacle (Big Tentacle • Baby Tentacle) • Wee MacTusk • (Poison Birchnut Tree • Varg )|
|Boss Monsters||Ancient Guardian • Deerclops • Spider Queen • Treeguard • (Bearger • Dragonfly • Moose/Goose )|
|Neutral Animals||Bee • Beefalo • Bunnyman (Beardlord) • Koalefant • Krampus • Pengull • Pig (Werepig) • Rock Lobster • Snurtle • Slurtle • Smallish Tallbird • Splumonkey • (Buzzard • Catcoon • Volt Goat )|
|Passive Animals||Baby Beefalo • Butterfly • Chester • Crow • Gobbler • Mandrake • Rabbit (Beardling) • Redbird • Smallbird • Snowbird • (Glommer • Moleworm )|
|Other||Abigail • Charlie • Maxwell • Pig King|