Apocalypse

Properties
Fires a nuclear missiles toward the nearest enemy structure. Nuke destroys anything in its area of effect and shuts down all shields in the entire map, including your own shields. Any asteroid caught in the blast will be destroyed as well.

While units that get caught at the center of the blast will most likely be destroyed, units around the edge of the explosion may survive, albeit receiving heavy damage.

Artillery, Mjolnir, and Apocalypse are the only turrets that target structures.

Nuke AOE radius is 5 tiles.

Obtaining Apocalypse
The only way to obtain Apocalypse (and Ragnarok, for that matter) is to play a level 10 (or higher) mission with it as a reward. Apocalypse does  NOT  appear in the store.

Using an Apocalypse
Make sure you got some defenses to keep enemies from your base (especially fast fighters which is the main problem).Try to place it on sides (not too front as in to avoid enemy ships getting to that) so it wouldn't be blocked.

The nuclear missile that an Apocalypse fires is extremely dangerous, to both your own base and theirs. Unless you're attempting to demolish enemy units,  DO NOT  let the Apocalypse hit an enemy unit. It will kill most units in the blast, including yours. It is advisable to use Constructors to place the Apocalypse farther away from your base to prevent possible disaster and hit the enemy base easier.

Using gladiators from a Fighter Yard is a good counter to the apocalypse (and ragnarok for that matter) as they have mounted phalanxes which destroy projectiles. Grendel also works but it is not reccommended as it has a higher cost (both when launched from star dock and naval yard) and naval yard launches them clumped together so they may all get destroyed in one nuclear blast.

Countering an Enemy Apocalypse
Make a lot of Fighter Bays with any fighter (except Miner and Engineer) and try to place them in such a way that the fighter will fly into the missile's path. Gladiator or other ship with mounted phalanx is also good. Also if needed, make a empty bay, turret, or barricade to block the shot. Prevent the shot from hitting your base at all costs. Due to how game mechanics work, nuke will ignore and phase threw any unit or turret that was crewated AFTER it was fired.

This can be exploited however to "dodge nukes". By placing a turret in front one the side as target for Apocalypse, then immediately sell and put it back (make sure there is nothing behind or infront that may collide or detonate the nuke).

If your base has already survived an Apocalypse hit, you can place a Phalanx where the Apocalypse fires at your base to prevent the blast from reaching your base entirely. This requires a surplus of Energy, however.

If you have a phalanx with 2x range mods along with 4x primer techs then it will be immune to the nuclear explosion. (Although it might still make it close enough to destroy it if there are any other projectiles in the range of the phalanx.)