Atrium

Atrium is a boss that was added on July 15, 2019. Later on, it was added secretly into the game.

Design
Atrium has a white triangle base with three drone spawners on each side and a Constructor cannon on top of the base.

Technical
Atrium has incredibly low health, (lower than ANY boss, testbed or otherwise), but fast speed. It has very powerful ammunition, blocks have a lot of penetration, damage, and speed but low health. Drones are very fast, have decent health and penetration, and do medium damage.

Spawning
Spawns by a randomizer.

Countering
When countering Atrium, remember, it has very low health, so charging is very effective. However, be careful. As a bullet spammer, you will not be able to penetrate the ammunition of Atrium, and as such it will kill you very fast. If you are a bullet spammer, it is the best option to run away in order to wait for boss to die. As a Pounder branch tank, you should get closer to Atrium and shoot your powerful bullet. Boss will die from a single bullet, so hit it by all costs. As a drone or minion user, charge all of your drones into the Atrium, and it will be dead. As a Trapper branch, you need to retreat, while creating a line of traps so that Atrium will hit all the traps and die.