Octo Tank

The  is one of the two current final Upgrades from the Quad Tank and is available to upgrade at Level 45. It cannot upgrade any further. On July 30th, 2016 both it and the Triple Twin’s health was nerfed.

Design
The features a circular body surrounded by eight evenly spaced Cannons (spaced exactly 45 degrees apart) that look exactly like Basic Tank Cannons.

Technical
Upon Upgrading:
 * Bullet Damage is decreased.
 * Reload is slightly increased.

Strategy

 * Strong Against: Multiple enemies, slow melee tanks, Drone wielding tanks.
 * Weak Against: High DPS, tanks with focused fire, Destroyer branch, fast melee tanks.

As the Octo Tank

 * Recommended builds for the include a glass cannon or general upgrades. A glass cannon build concentrates on Bullets and not on health Stats, and is vulnerable to fast moving rammers such as the Booster. Using C+E is highly recommended to create a nearly impenetrable zone of bullets. This works well for farming Polygons, too.
 * An with general upgrades can generally defend well against anything, but is vulnerable to Machine Guns, Gunners, and any other tanks with high Reload and maximum Bullet Penetration.
 * An unskilled Tri-Angle or a Booster can be easily destroyed by an without taking much damage in return, due to the Octo Tank’s massive firepower..
 * Players should maximize their Bullet Penetration to balance their vulnerable body if they have low Body Damage, but should beware of Boosters as they may have very high Body Damage which might kill instantly. However, players can also try and catch unsuspecting prey by increasing Max Health and Body Damage along with Bullet Speed and Movement Speed.
 * Beware that the only fires one Bullet in each direction, so it’s not very easy to combat high RoF tanks, such as the Machine Gun, Sprayer or Triplet. If you turn on both auto keys, you can slightly counter the attack.
 * As the in any team mode, if you max your Bullet Penetration and Damage, and head to the Pentagon Nest, you can act as a shield for the whole area. An  needs its team too or else it will be vulnerable as someone could kill it easily using a Twin-class or Gunner-class tank.
 * You can counter low-Level Snipers with not fully upgraded Bullet Stats, but not Destroyers, Hybrids, or Annihilators.
 * In Team modes, try to make a team that includes at least one Trapper, one high DPS tank like the Triplet, and one Drone user. This will maximize your chances of survival, as these are all tanks you would have trouble killing if they were the enemy.
 * Players should get at least 3 or 4 people on their team to gather near the enemy base, and become . Then, they should turn on Auto Spin and Auto Fire. This will force newly spawned players to stay in their base, while others can kill the better players on the enemy team. Be wary; this may cause a degree of lag. Even Triplets and Sprayers will be unable to touch the team, and only another team of high RoF (Rate of Fire) tanks will be able to counter the Octo Tanks.
 * This tank is suitable to play in the FFA gamemode because with eight cannons, it is able to counter multiple enemies at once.
 * The Octo Tank is also a good choice in Survival, as the bullet storm can take down most enemies from upgrading to a class that may take down an Octo Tank like the Annihilator or Triplet.
 * A build with no Bullet Speed can make a "hurricane" around the Octo Tank if the Octo uses C+E, making it hard to dodge an Octo Tank. The Octo Tank can chase down enemies with a bullet shield, blocking any enemy bullets. This can be effective against snipers and also effecttive for finding any invisible tanks, like the Manager.

Against the Octo Tank

 * This can be very dangerous due to the Cannons surrounding it making it harder to approach. However, an easy way of defeating an is to use any focused firing tanks with max Penetration and shoot in the little gaps between the Cannons.
 * To counter an, use tanks from the Destroyer or Sniper branches. The ’s bullets can’t counter the destroyer or sniper’s strong Bullets, so you can easily hit and kill it.
 * Alternatively, a skilled Tri-Angle or Booster can dodge the storm of Bullets, and ram the between the Cannons. Beware when there are other tanks around, as ramming the  will leave you low on health.
 * An Overlord or Overseer can use their Drones to flank the through the gap between its Cannons, but most of the time, if the Octo Tank has high movement speed, it can get difficult to do this.
 * Heavy concentrated fire from the Machine Gun or the Sprayer can easily wipe out an overlooking . A high rate of fire combined with a strong Bullet Penetration will obliterate the, as it lacks concentrated fire in one direction.
 * Using a Triple Twin is acceptable against an Octo Tank, however, because a Triple Twin’s Bullet Penetration and Damage is lower than that of a Twin’s, it isn't really recommended.
 * Penta Shots work quite well against s. The high DPS and slightly-concentrated fire of the Penta Shot can easily out-penetrate the ’s, while decreasing the chances of flanking if/when the does Auto Spin and Auto Fire.
 * Trapper classes can block incoming Bullets and slowly approach the, and thus harm it. A good example of this is the Mega Trapper, which can shoot huge, high damage Traps to push to the . This however, is a highly skilled technique.

History

 * In very old versions of Diep.io, the Max Level was 60, and the path to get the was like this: Tank → Twin → Triple Shot → Quad Tank →.
 * Therefore, at that time it was a Tier 5 tank.
 * Before August 15th, it branched off the Twin Flank at Level 45, it was then removed by it’s upgrade and replaced with Battleship. It now only branches off Quad Tank.

Trivia

 * The Octo Tank has the second most Cannons.
 * The one with the most is Spread Shot.