Bomber

Bombers are enemies wearing a Plague Doctor mask and able to fly by using a jetpack on their back. These enemies are only found in the Ossurary at 2-3 BSC and the Astrolab, making them fairly rare.

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

If the player is right next to the Bomber when they detect you, they will use their melee attack. Any further and they will fly and use their dive attack. There is a cooldown before they will use their dive attack again. If at longer distance and they can't fly, they will throw bombs instead.

Elite Bombers can spawn with any of the Elite special abilities. They are particularly dangerous when they have the rotating laser and the clone Elite abilities.

Strategy
Bombers are dangerous due to how persistent they are. Once they start flying, they will chase you for a very long time until they are in the spot to do their dive attacks. However, once their land their other attacks are easily to avoid. Their melee attack is slow and predictable, and their grenade attack has a long startup.

To dodge the dive attack, wait for them to fly directly above you, and focus on the distance between you and the Bomber rather than their attack cue. If you do it too early, you can get hit by it. You can outrun the dive attack if you have a speed boost and with enough vertical space. Standing still and waiting for them to attack makes it easier to time the dodge.

Bombers are especially dangerous when you're fighting multiple enemies, making it much harder to avoid their dive attack. If you manage to draw aggro from a Bomber and other enemies, run away to give you space between you and other minions far from their reach, then deal with the Bomber before the other minions can catch up to you.

Avoid fighting more than one Bomber at a time. There's a good chance that when you dodge roll one of them, one the other will hit you. Their detection range is not as good as ranged minions, so you can always wait for one to see and chase you then run away from the other enemies and deal with them one at a time. Use the Homunculus Rune if you want to be safer.

You can interrupt their flight by attacking them while they're try to fly above you using some crown control effect or a strong single hit skill. While you can do this with attacks, it's not guaranteed and leave you open to get hit if they do manage to fly above you.

Aura of Laceration and Wave of Denial are very powerful against Bombers. Aura of Laceration can kill them before they can even do their dive attack, and Wave of Denial has a very high chance of interrupting them, or at least put them back to be too far away to dive attack.

Trivia

 * Bombers were added with the v1.2 update, aka Rise of the Giant DLC in March 2019.