Monster

Monsters are hostile mobs that can be found throughout the game. The first ones you will likely see are the spiders. Most monsters will attack the player on sight. Monsters tend to drop items useful to the player, and thus, even though it is a possible danger, the player will most likely have to seek out these creatures. Some are stronger than others. One can expect to defeat a small spider nest on day one, if he or she manages to research and craft a spear, while one shouldn't attempt fighting a Swamp Monster until the player is extremely well-prepared, as it can kill a player in two swipes without armor.

Guide to Creature Aggressiveness
. Wondering when a monster will stop chasing you? It will if it can't manage to hit you in the first place. Everytime a monster attacks, its "aggro", AKA it's willingness to continue to chase after you, refreshes. Therefore, unless you outrun it, it is going to chase you infinitely until either you or it dies. It is with some monsters completely impossible to use outrunning them as a strategy, and thus one should either consider taking up the fight or equipping an amulet, if the player has one.

This video shows the basic idea of how a Beefalo and its herd will chase you in attempt to defend itself.

A monster will chase you for around seven seconds, upon which it will stop doing so. If a monster however does manage to take a swing at you within the seven seconds, it will continue to chase you until you die.