Icon of Sin (Doom Eternal)

The Icon of Sin returns as a boss in Doom Eternal, based on the boss of the same name in Doom II, and is the final antagonist of the game’s main campaign. The Icon was originally created using the heart of the Betrayer's son, as Hell's twisted way of honoring its bargain with the Betrayer to return his son to life. The Icon of Sin previously slumbered in Hell's Necropolis in Doom (2016), where it could be found as a dormant demonic edifice.

Tactical analysis
The battle takes place atop a ruined skyscraper on Earth. Unlike its form in Doom II, the Icon of Sin in Doom Eternal has a full body and can attack the player directly by slamming its fists down on the arena, shooting fireballs from its forehead, or sending out waves of fire; it can also summon other monsters to assist it.

Phase One
In the first phase, the player must attack eight different areas on its body - the right pectoral, left pectoral, right shoulder, left shoulder, right hand, left hand, belly, and head - in order to break off its armor. Shooting parts of its body which are already unarmored has no effect, so accurate weapons such as the heavy cannon and ballista are preferable for breaking its armor. The Icon's movements become faster and more aggressive as its parts are broken, so the smaller parts that move around more frequently (such as the hands) should be targeted early before they become more difficult targets.

The Icon of Sin will regularly summon monsters ranging from Fodder up to Super Heavy demons with the Baron of Hell being the only one from this category to be summoned. At certain intervals the Icon of Sin will eject Argent energy on the field which causes damage to the player if they stay in place and will destroy the monsters summoned. Normally this causes different breeds of monsters than those that were present to be summoned next. The Icon of Sin will at times eject flames from his hands and incinerate certain areas which will cause damage if walked on. He can also utilize magical attacks from his head ranging from a magic circle which moves forward like a projectile, or a torrent of fireballs. Both of these attacks can be blocked by being behind walls, with the magic circle having a particularly large hitbox, so the player can attack the Icon of Sin while the circle is dispelled on contact with a wall.

Of the two phases, the first phase is arguably the most dangerous as there is more limited room to maneuver, and the Icon of Sin is more prone to employ its physical attacks which can do significant damage and even catapult the player away, causing potential disorienting or even launch them far away from the building resulting in fall damage. The player should pay attention to the Icon of Sin's movements and dash away if it raises its fists as it will typically signal it will slam at the player's position.

There are multiple goodies on the arena ranging from medkits, armor pieces, ammunition and most vitally Crucible and Blood Punch charges. The latter two will recharge over time and will respawn allowing the player a vast supply of both, therefore the player should employ both to deal with troublesome monsters like the Baron of Hell or Cyber-Mancubus or Pinkies. They can also be used if the player is low on health as it will provide some quick emergency health drops. Some other items like armor also regenerate but not as frequently. There is also one Soulsphere which requires bar jumping to get. Employ the Chainsaw, Flame Belch and Glory Kills as needed to refill.

The best way to damage the Icon of Sin is through the BFG-9000 as it will cause severe damage to any body part it hits while disposing of the horde of monsters in the area. It should be noted however, that the plasmic ball has to hit the Icon of Sin to cause damage or else its effect will be fundamentally null. It is best used to hit easier targets such as its torso, head or stomach, although it could also be used on its hands after an attack (however, at point-blank it risks not being as useful in general). Three charges are available on the map, so if the player has conserved their BFG-9000 ammunition they will be able to get several shots in this phase. Plasma Rifle, Ballista or Chaingun are good and fast ways to deal damage as well. The Rocket Launcher and Super Shotgun might also work for the shoulders and hand, but the player should use them on closer proximity. Some jumping platforms can be used to get to the side edges of the arena and even to send the player to the air where they should have a better view, while avoiding some of the demons. After the parts are destroyed the Icon of Sin will launch some fireballs before retreating into a portal.

Phase Two
In the second phase, the battle moves to a different building and the Icon can walk to different sides of the arena to attack. In this phase the player must attack each part of its body again, this time destroying its flesh and exposing the bone and gore underneath; as before, attacking a previously broken part of its body will not do anything and the Icon will speed up with each broken part.

The Icon of Sin is a less threatening adversary per se in this phase as there is far more room for navigation, so the player is less prone to its physical attacks. However, some changes in behavior can compensate for this. The Icon of Sin will at times rise its fists which will cause a rain of fireballs to fall down in the area at random places. Another attack has the Icon of Sin charge energy before unleashing a massive beam from its head which can deal massive damage if one remains on the laser's path. In conjunction with this, the Icon of Sin will use a more selective pool of monsters, typically preferring the use of Barons of Hell, Revenants, Mancubi (both kinds), Arachnotrons and Whiplash along the usual fodders.

Generally the same principles as Phase One apply. Use the Crucible and Blood Punch refills to deal with the monsters, whether to take care of threats or also to get some much needed health. Use your equipment to refill health, armor or ammo as needed. BFG-9000 charges and Soulsphere are also present in this map (and as equally limited), the former will help with damaging the Icon of Sin. Even with the more ample space, the player should stay on movement at all times to avoid being surrounded by mobs, keep track of the Icon of Sin and also to refill Crucible or Blood Punch which will be crucial for survival. The jumping platforms will provide the best help to the player to avoid the demons and allow the player to aim and shoot at the body parts better.

After the last part of its body is destroyed, the Icon collapses on the arena and the player stabs its exposed brain with the Crucible, killing the Icon of Sin and its evil once and for all.

Lore


Ancient Sentinel prophecies predicted the eventual return of the Titans, who persisted in slumber in Hell, seemingly immortal. As one of the Titans, the Icon of Sin is a force of chaos and destruction, and is considered a sign of the end times. The Icon of Sin in particular is described as being "forged from the essence of human suffering".

The Night Sentinel Commander known as the Betrayer, in an attempt to free his son from his torment in Hell, made an agreement with the Hell priest Deag Grav to lead the forces of Hell to the Elemental Wraiths in exchange for his return. Instead of giving back the son as expected, he returned in the form of the Icon, and Argent D'Nur was crushed and absorbed into Hell. The son's soul is said to be bound to his still-beating heart, which ties it to the Titan.

The Icon of Sin was resurrected by the Khan Maykr following the Doom Slayer's execution of Deag Grav, the final Hell priest, in a bid to continue the consumption of Earth. She constructed its Maykr-designed suit of armor in a bid to make it indestructible and to allow her to control the beast. However, when the Slayer destroys the heart of the Betrayer's son and frees his soul, all control over the Icon of Sin is lost, and it is said that if it is allowed to continue existing, it will eventually consume the entire universe, creating a super-massive black hole which will draw all of existence into Hell to be corrupted.

Trivia

 * The Icon of Sin's figurine is unlocked automatically after collecting every other figure in the game.
 * The Icon of Sin has clawed feet that are not normally seen during gameplay but can be seen in the model viewer, accessed by activating his figurine.
 * The Icon's "meteor rain" attack strongly resembles an attack of the Maledict and is of similar threat level.