Lephantis

J-2000 Golem is a massive infested boss introduced in update 10. It was originally going to replace J3-Golem but was moved to the new Orokin Derelict tileset instead. J-2000 is also the hardest boss to encounter, as parts for the key that takes you to the assasination level on the Derelict requires parts only obtainable from other Derelict missions, which require keys and parts themselves.

Appearance and Abilities
J-2000 Golem is a massive, three headed creature with several limbs. The three heads are different in appearance, they also have their own name, one being called "infested Corpus" which has two tentacles either side of it's mouth, another called "infested Grineer" which has 3 jaws, two arms to wield a scythe. The third head is called "Ancient infested" it has a stout and long jaw but not as wide as the others. All three heads are connected to a large ball shaped body, which has three legs positioned like a tripod.

It has the ability to stomp which causes a shockwave knocking back any nearby warframes, It also is able to spit poison at a great distance, far more poison then J3-Golem. It also wields a large scythe which resembles a massive version of Hate, but covered in Infested biomass.

J-2000 Golem, uses the exact same taunts as J3-Golem.

Upon entering the room with all players, a cutscene will play, being a giant head(Ancient Infested) that pops up from the ground, opening its mouth and disappearing into the ground.

The Tenno will then be left standing in an empty room, waiting for the heads to appear again. The heads burst through the ground and knock down anyone who was standing too close. There are 3 different heads, each with its own weakspots and attacks:
 * The Infested Corpus head spits poison clouds and its weakspot is the bright red section in the middle of its "mouth" that opens and closes. You can only hit it when the mouth is open. The poison clouds are similar to those of J3 golem but are much bigger and thus more dangerous.
 * The Ancient infested head sometimes launches "spikes" in a dispersing formation (ie the spikes all move away from the mouth/gun and spread out) these projectiles will detonate on impact. Its weakspot is the bright red section of its neck, however, you can only damage it when it opens up (similar to a cobra's head).
 * The Infested Grineer head wields a giant scythe and will takes swings at you. The swings can be evaded and jumped over if timed correctly. This one possesses two weakspots: one on its center torso and the inside of its mouth. The weakspot on its torso appears to be a Grineer's face.

Each head will drop a mod, Energy/Health orbs and quite a lot of ammunition when defeated.

After defeating every head, another cutscene will start, showing an ornament from the ceiling falling down and breaking the floor, followed by the Tenno landing in a lower level.

There will you face the actual Golem, which consists of all three heads mounted on a large bulbous body with 3 massive legs, positioned like a tripod. The heads will behave exactly like they did before. If you get close to Golem he will slam its body into the ground to knock you down. All three heads are positioned outwards so you can only face one head directly at a time. The only way to defeat Golem is to defeat all three of its heads. The best way to do this is to all focus on 1 head at a time, then move on to the next one. If you stand directly in front of 1 head, the other 2 will barely be able to hit you (but they will still try).

During the second stage of the battle, infested spawn pods will appear in the arena, occasionally spawning in chargers, leapers and runners. Due to the long nature of the battle, it's best to keep the pods alive so they can keep spawning Infesteds to drop ammos and or energy orbs.

Strategy

 * Aim at the weak points. You will notice it opening and closing, it also has a distincitive red colour, therefore it cannot be missed.
 * Frost's freeze ability can be helpful when dealing damage to Golem with severe lag.
 * A good rule of thumb is to aim at a head's weakspot when it winds up to attack and focus fire while dodging or jumping over the attack itself as all the heads are guaranteed to take damage during their attack animation. Only the Infested Corpus head seems to make itself vulnerable without following up with an attack.
 * Using a Rhino against this boss is really effective due to the slow-motion effect of Rhino Stomp, which allows you to deal damage to the weakspots for longer periods of time. Be sure to remember the proper cues for the weakspots as a poorly timed stomp will simply extend the invulnerability periods and waste the duration of an active Roar. Also note that the Ancient Infested and Infested Grineer heads' attacks will remove Iron Skin very quickly and Rhino may miss a vulnerability window if he is knocked down.
 * Using a Frost is almost as efective as using Rhino due to using spam of Snow Globes on Golem, which allows you to deal damage to it's weakspots for long time.
 * In phrase 2, there will be elevated platforms in the circular field, the infested Gineer usually have trouble aiming which could be used as an advantage
 * Strategy as to which head to take out first in lets say a solo mission would be the ancient infested due to the poison bombs/grenades, the infested corpus to stop spawning mobs and finally infested gineer which only does melee

Bugs

 * Taunts currently use J3-Golem's picture as a placeholder.
 * Name J-2000 Golem is showed only to host of mission. Other players will see it as J-3 Golem.
 * There is Currently a bug whereby on laggy games only the host will be able to damage to golem with weapons. Though this may happen all abilities still work successfully including Damage abilities such as antimatter drop and CC abilities such as Rhino Stomp. You can thus still contribute to the fight.

Trivia

 * This boss rewards the parts blueprints for Nekros, the new warframe added in update 10. The blueprints don't drop as purple orbs as usual, but are instead given to players as a reward at the end of the mission. You are guaranteed to get a blueprint if you complete the mission (but there is no guarantee you will not get the same blueprint over and over again).
 * J-2000 Golem was created after J3-Golem, and judging by the same name, through the same processes.
 * The J-2000 Golem has 2 stages of combat, the first stage is where you will fight the 3 heads. Upon defeating all 3 heads, you will drop below of the stage and fight the 'real' J-2000, a massive walking infested creature with 3 heads.
 * Underneath the infested Grineer head there is the face of a person; It's unknown who's face it actually is. This is akin to Dark Sector's boss Mezner who also is fought in a large arena type area, and who's face is distorted and stretched over the infested creature.
 * Golem Nav Coordinates can be found in lockers and crates throughout the mission, allowing to recuperate some or all of the Coordinates used in crafting the assassination key.
 * The J-2000 is always level 50
 * Should you point your mouse over the central body during the second stage you will se an indicator of total health (%age health of all the heads) this gives a good indicator of how much of the battle there is left to fight.