Argos, Planetary Core

Argos, Planetary Core was a massive Vex Hydra that was found trapped within the Leviathan's core. It was a unique Axis Mind whose size is comparable to that of Panoptes, Infinite Mind. It was the final boss of the Leviathan, Eater of Worlds Raid Lair.

Overview
While Leviathan consumed chunks of Nessus to convert into Royal Wine for the emperor, the titular Planetary Core was sucked into the Leviathan's belly alongside squadrons of Vex, to which the Vex Mind generated a massive barrier surrounding it and the nearby debris from the planet. Argos' barrier quickly began to clog up the Leviathan's massive vacuum and stalled its engine.

Meanwhile, a curious fireteam of Guardians stumbled their way aboard the Leviathan where they decided to branch off their natural surroundings to navigate the massive engine beneath it. Taking notice of the group of Guardians within the ship engine, Emperor Calus calls off his Loyalists and invites them to destroy the fearsome Vex mind. The raid team makes their way into the belly of the beast, where they exposed Argos from its outer casing using the cranium weapons leftover by its Vex brethren. Argos' destruction caused its barrier to dissipate and the ship's engine threatening to consume the surrounding debris, including the Guardians. Calus would intervene and transmat them to safety, to which he would promptly reward them for their tenacity in ridding his ship of the Vex.

Gameplay
Argos' encounter was structured very similarly to Aksis, Archon Prime, and is split in two phases.

Break the Barrier


Initially, there would be a giant prism structure floating in the center of the triangular map; it was be protected by a barrier that will need to be brought down by shooting its Arc, Solar, and Void crystals. These crystals could have only been destroyed with its respective Vex elemental cranium weapon, which must have been obtained by elementally charging Vex Craniums scattered around the map in altars which were found in the center of each major island; with the front (which was the spawn point for both encounters) being Void, the back being Solar, and the right being Arc. These fragments needed to be inserted into one of the corners of the altar, and the elemental cranium weapon would appear after the cranium rested within one of the altars for ten seconds. This process was up against two impediments: masses of lesser Vex units and the triggering of Quantum Mines. If it took too long to destroy a crystal, then the mines would arm themselves and eventually detonate, wiping the entire team. Successfully destroying all the crystals broke the first layer of the barrier, finally revealing Argos, Planetary Core.

Destroy Argos


With its full form finally revealed, Argos began to attack with its Aeon Maul, which had greater range and rate of fire than those wielded by normal Hydras. It was protected by a prismatic barrier that could have only been disabled by bringing the floating elemental charges on the top, left, and right corners in line with a switch at the center, again using the respective cranium weapons, which was obtained in the same manner as last phase. When the barrier was shut down, Guardians gained the "Unstable Energy Boost" buff and was able to freely damage Argos. However, they had to remain alert, as Argos would activate one of two self-defense protocols. It could fire a detainment prism from its eye, trapping anyone that it touches and sending them away from the main platforms, eventually killing them via Force Cage unless a teammate shot the cage and freed them. Additionally, it could send a barrage of Supplicant missiles, which would promptly seek their targets out and blast them apart unless they were shot out of the sky before they could hit their target. After a short while, the prismatic barrier would re-calibrate itself and fully shield Argos once again. However, it would occasionally bring down the barrier on its own volition and attempt to rip the air apart with Void energy, signaling the charge-up of its Gravity Smasher bomb. If left to detonate on its own, it would instantly kill the whole team. The only way there was to shut this process down is to, from the surrounding semicircular platforms, destroy a pair of weak points that would be open: one on its middle segment arms, one on its head, and one on its back. Destroying any given pair of weak spots would briefly stun Argos, allowing some damage to be dealt, but it was recommended to get back to gathering craniums to initiate the damage phase again as the this damage phase was not only short, but could have killed a teammate as the shield re-generating pushed all Guardians away from Argos, possibly sending some into unfavorable situations or off the map entirely.

Prestige Mode Changes
In Prestige Mode, players had to play with a set loadout of weapon types, e.g. Kinetic Pulse Rifle, Energy SMG, Power Grenade Launcher, and ammo reserves were disabled as well. You started with only a full Kinetic magazine and as soon as you emptied it, the Energy Magazine is refilled, after that the Power Magazine. Sometimes it may have refilled two Magazines, and it would only cycle on as soon as every magazine has been emptied. Additionally, ammo drops were limited to rare drops of Heavy Ammo.

Quantum Mines now took 25 charges before being destroyed.

Enemies in general were harder to kill and dealt more damage.

Trivia

 * The two main Vex Minds seen in the Curse of Osiris expansion, Argos and Panoptes, were named after the same character of Greek mythology. Argos Panoptes (also transliterated as "Argus") was a many-eyed giant who worked as a guardian and spy for the Olympian gods due to his ability to see everything at any time.
 * Argos was the largest Hydra ever encountered by Guardian forces, easily among the largest Axis Minds.
 * Argos was the third largest Raid boss, behind Oryx, the Taken King, and Riven.
 * It is unknown if Argos was the core of Nessus, or the core of a Vex world previously consumed by the Leviathan. If it hailed from Nessus, then its destruction likely stopped or at least temporarily halted the conversion of Nessus.
 * Argos was one of few raid bosses that had multiple encounters. Among them being Templar, Aksis, Archon Prime, Vosik, the Archpriest, Insurrection Prime, Kell's Scourge and Consecrated Mind, Sol Inherent.
 * Argos had a strange translucent arrow that it stuck out of its head under its eyes that resembles a tongue. Its unknown why Argos has this as it's the only Vex seen having it.

List of appearances

 * Destiny 2
 * Curse of Osiris