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.

Doing the boss solo is discouraged as it may be difficult for some players, as the constant poison, electrical hazards and enemies can kill players who are not careful.

Appearance and Abilities
J-2000 Golem is a massive, three headed creature with several limbs. The three heads are different in appearance, and they also have their own name. One being called "Infested Corpus" which has two tentacles on either side of it's mouth, another called "Infested Grineer" which has 3 jaws, and two arms to wield a scythe. The third head is called "Ancient Infested," and it has a long, stout 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 is also 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 where Infested Corpus head will pop up from the ground, open its mouth, and disappear 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 their own weakspots and attacks: Usually they appear in the following order: Infested Corpus, Ancient infested and Infested Grineer.
 * 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. During the second stage of the battle, the corpus head will occasionally spit out projectiles that turn into infested spawn pods when they hit the ground. These will spawn infested chargers, leapers and runners. They can be destroyed but consider keeping them alive so the infested spawned can be killed for ammo drops.
 * 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 stick were they land then detonate a few seconds after landing. They are easily avoided but can do serious damage if you stand to close and get hit by multiple explosions. 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 take 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 one 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, you will 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 the Golem, it 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 for all players to 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).

The puddles of water in the second arena are electrified, so stepping in them will damage you just like the fire hazards do.

Stats
[1]per boss part, including the second phase of J-2000 Golem.

[2]These parts have no armor.

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.
 * It is not recommended to use weapons like Ogris, Torid, and Acrid. The majority of these weapons' damage (explosions and DoT) target the torso of an enemy, so you will lose a lot of potential damage even if you're aiming at weak points.
 * The use of the Infested Impedance aura can significantly improve your chances against golem, as it slows all infested by 30% at max rank (including attacks), allowing you to evade his attacks easier and hit his weakspots for a longer time. Of course you will also have to wait longer for them to open.
 * 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.
 * As with previous bosses, Rhino is the best suited to solo runs due to the effects of his abilities. Iron Skin will negate almost all sources of damage and CC in the fight and allow him to focus on hitting weak spots, Roar will allow him to deal more damage while the weak spots are exposed and Rhino Stomp will keep them open for long periods of time. Do note that he still needs defensive mods to mitigate the heavy incoming damage when recasting Iron Skin.
 * 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.
 * Iron Skin will be removed very quickly if Rhino simply stands still to deal damage and if it breaks at the wrong time he may miss a vulnerability window or even die if he is knocked down.
 * Using a Frost is almost as effective as using Rhino due to using spam of Snow Globes on Golem, which allows you to deal damage to its weakspots for long time. However, Frost does not have any means of blocking environmental damage and the crowd control effects of Golem's attacks.
 * In phase 2, there will be elevated platforms in the circular field. The Infested Grineer usually has trouble aiming which could be used as an advantage
 * Using a Rhino and a Nova along with High DPS weapons, you can kill each golem head during the duration of a single Rhino Stomp if timed well. If successfully used, this technique makes the boss very easy to defeat. You do still have to watch out for the electrified water and the regular infested however.
 * Since Golem's attacks deal damage in a large area and many of them are poison, your sentinel probably will not survive the fight if you cannot succesfully dodge every attack.
 * A Nova can be handy against this boss. Molecular Prime slows down the Golem, allowing your team to shoot the weak points for longer periods of time. The double damage will also help take the Golem down.
 * Be carefull for the knockdown of the Grineer head and the body slam. They may knock you into a poison cloud/electrified pool and cause severe damage before you are able to get up and run out of it.
 * By using Banshee's Sonar ability you can manage to get an "orange" spot at a weak point, which would greatly increase the damage deal to that specific part in the weak points you should be dealing with. This strategy isn't as useful as the other strategies described above: the enemy will get highlighted randomly across the body, since this boss is the largest amalgamation by this point, the orange weakspot would normally cover shielded body parts, like the back or the legs of the monster.

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.
 * Currently, there is a bug where on laggy matches, only the host will be able to deal damage to the Golem with weapons. All abilities still work properly including Damage abilities, such as Antimatter Drop and CC abilities like Rhino Stomp, so you can still contribute to the fight.

Trivia

 * This boss rewards the blueprints of components for Nekros, a 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 get a different blueprint each time.
 * There is no way of determining what blueprint you get. The theory that you get a blueprint depending on which head you leave as last or on the order in which you kill the heads has been tested and proven false by numerous players.
 * Underneath the Infested Grineer head, there is the face of a person; It's unknown whose face it actually is. This is akin to Dark Sector's boss Mezner who also is fought in a large arena type area, and whose 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 see an indicator of total health (percentage health of all the heads). This gives a good indicator of how much of the battle there is left to fight.
 * It is possible to ride the J-2000 Golem by jumping from the platforms or by using powers to get onto its back. However, the Golem has a tendency to knock you off, dealing damage.
 * If you listen closely, the J-2000 Golem's taunts sound like an edited version of Kril's.