The world of Wyvern has many kinds of monsters in it. These types of monsters have various abilities, threats, and behaviors that adventurers should know about, lest they find themselves paying a surprise visit to the chapel.
Generally, individuals of the different types of monsters don't vary from one another. For example, one rat has identical stats as another rat of the same type. On the other hand, some monsters--especially humanoids--will wield weapons that may make an individual stronger than another without the same gear (lucky for you, this gear will drop when you kill them). In some circumstances monsters may even spawn with melee or ranged weapons, and in the case of the latter weapon it will actually cause them to behave differently.
Monsters have different behaviors depending on their weapon type, their aggression, and the detection of an enemy. Generally, monsters will roam around slowly with no particular pattern when there is no threat detected. Some monster types don't move until attacked, yet others are simply always stationary. When an enemy is detected, most monsters will begin attacking the enemy immediately. In the case of a monster equipped with only melee gear it will rush towards the enemy as best it can, while in the case of a monster with ranged capabilities it will try to stay out of the melee while firing.
Monsters fall into three categories when it comes to determining if the player is an enemy or not:
- You have to attack it to get it to attack back
- If you bump it or hit it with a spell or otherwise anger it, it will attack
- It always attacks the player on sight
Different monster types vary in their detection capabilities. For example, some monsters are very good at seeing an invisible player, while others may not be able to detect them from just one tile away (but even in this case they will attack back in melee range). Some neutral monsters can even detect if one of their allies are under attack, and will turn hostile to the threat. All monsters can see the player from 7 tiles away (? with my viewport size, if I can see them, they can see me).
Most monsters will spawn as a common version of themselves, however, there's a chance that they may spawn in as a "badass", which will have more hp and will hit harder. In this case, the monster will be displayed a much darker shade of its common kin, and will show up with a "Badass" prefix in the combat log.
I have also heard of named "boss" monsters, but alas, I have never seen one with my own eyes. (if someone knows the info on this, feel free)
Monsters fall into different levels of "threat". It roughly translates to the "level" of a monster, in the same way that a player has a level--but the player and monster "level" are not necessarily meant to be equal. Other than being used as a rough estimate of the difficulty of a monster, the primary use for a monster's threat level is in Random Dungeons. The deeper you go, the higher the threat level of the monsters.