Demon

Demons are orange flying gargoyles that mostly dwell in the Cavern. On very high difficulties (4 BSC and above), they can also be found in the Slumbering Sanctuary and High Peak Castle.

Behavior
Demons can detect the player through walls and platforms. They have at higher vertical detection range than horizontal.

Once it detects the player, it will fly towards them then either uses its melee attack or shoot fireballs.

Demons are immune to burn damage over time.

Strategy
Demons are fairly squishy, but are dangerous if you're not able to ambush them. They are very mobile once they are aggroed, their attacks come out fast, and they can constantly move while attacking you at the same time. It's way better to kill them before they can react. While they can detect you from different platforms, their reaction time is fairly slow and should give you enough time to run up to them.

Ranged weapons are very effective against Demons as they can hit it out of its flight easily. If you don't have a ranged weapon, you will need either a shield to parry its fireballs or some kind of crowd control (Freeze/Stun/Root) or any sort of cooldown skill that can reach them and hit it out of its flight. Otherwise, they will be much harder to fight.

When a Demon approaches you from below, there's a higher chance it will start with its melee attack. Also, it cannot shoot fireballs an an angle higher than them. Therefore, they are easier to fight when approaching from above.