AWP-39, officially Advanced Weapon Platform 39, is an all-powerful TESTBED boss known for its role in lore and the insane amount of power it wields.
Design
The AWP-39 has a square base with one square and one equilateral triangle on either end, visually similar to a boat. It has one Hypercannon, which instantly kills anything and has the fastest rate of travel of any bullet in the game.
Technical
Even though at first it maybe seems easy to beat, it has 5000 health. Its original author was Rodrigo Rodrigues.
AWP-39 shots a yellow bullet with high speed, high reload and high damage that can one shot almost any tank in game (even Arena Closers)
The hypercannon also appears on many other AWPs later on (but they have less power).
On the Arena Closer splash page, you have the change to find the message containing a link to an image. That image also plays a role in the lore of the game. The link is
http://woomy-arras.io/img/unfixable.png (PLEASE DON'T SPOIL IT FOR YOURSELF. SPOILER ALERT)
Strategy
Even the author and the developer agree that there is no way to defeat the AWP-39 due its immense health and power. the AWP-39 has a high reload and high damage, and can theoretically kill Arena Closers. However, VPN may work against it although it would take a long time.
Gallery

AWP-39 in all its glory