Arena Closer

The Arena Closer, also known as AC, is an invincible tank that is primarily used to close arenas. It is also playable by developers. It comes in many normal tank variants as well as some TESTBED variants, though each bullet is invincible and instantly kills anything it touches..

Variants
The wording in patches 12/18/2018 (2) and 11/10/2019 (1) is vague, so many types may not be in the list.

Normal Tanks

 * Basic
 * Twin
 * Sniper
 * Poison Closer
 * Minishot
 * Hybrid Closer
 * Arena Closerception
 * Octo Arena Closer
 * Closerceptionist
 * AC-3

TESTBED Tanks

 * HOT WHEELS
 * Stweamwinder
 * Arena Summoner
 * Absolute Cyanide

Spawning and Behavior
Arena Closers spawn when a server has reached the maximum uptime or if a game mechanic causes it to occur prematurely, as in 4TDM Mothership or Portal Domination. Up to 8 arena closers may spawn of random types. Usually, Basic, Twin, and Minishot are the most common or even only arena closer variants, though other variants may spawn with less chance.

Arena Closers spawn outside the map, and move quickly towards the center, killing anything in their path including invincible players, bases, and owned dominators. Their bullet damage is indicated to be 10 million, per Patch 5/22/2018 (1), rendering all defenses useless, even Sandman Stabilizer Bullets.

Technical
Arena Closers are invincible and fire very fast, very powerful bullets at a very high reload rate. Arena Closers themselves, kill any tank instantly using body damage and are as fast as the bullets they fire. They can move over rocks, though bullets bounce off rocks like other bullets.