PvE
Agon is populated with monsters and wildlife you can kill.
Spawns
A spawn is where a group of monsters hang out. Some monsters do not travel far from the center of their spawn, others do. Monsters like kraken and Fire Dragon can travel more than a km from their spawn center.
On the map it will show the name of the toughest mob in the spawn. But if hoving mouse over it you can see all that can spawn.
Friendly fire
Monsters can sometimes hit each other, and if they are not immune to the damage type they hit each with, they take damage.
AI
The monsters AI can be very smart at times, like if they see you draw a bow they start sidestepping. They also seldom stand still when in melee, but circle around the player.
Most do not go into water when chasing a player.
Skills
Most of the monsters combat skills is same as those available to players. There is some exceptions, like the kraken attack, the dragon breath, golems that cocoon, hitting without a weapon drawn or ghosts that teleport when you get in melee with them.
Sneaking
When you crouch you can with some monsters reduce their detection range.
Jumping
Opposite of crouching, this is a sure way to get their attention if in range.
Blocking
Be careful, you cannot run through monsters, so you might get blocked in or a passageway to safety in a dungeon might get blocked.
Monsters will block some seconds even after they are killed and their body goes away.