Diablo (Diablo III)

Diablo is the final boss of of Diablo III.

Overview
The final battle with Diablo takes place atop the Crystal Arch of the High Heavens after fighting your way through the Silver Spire to reach the Pinnacle of Heaven at the end of Act IV. With all seven Evils embodied in him, he is not an easy fight. Followers cannot go with you to the fight against him (except in Adventure Mode), so prepare yourself accordingly.

The battle consists of three major phases, each of which can last as long as needed (as Diablo has no enrage timer). There are two Health Wells on the left and right sides of the central ring, but they are not available in phase 2.

I Am Legion: Diablo has five major attacks over the course of the battle, along with some supporting abilities. While he looks pretty agile, he is actually moving and attacking very slowly, compensated by his high damage and ability list. The Realm of Terror: After suffering enough damage (about 65%), Diablo stuns you and shunts you off to his Realm of Terror, essentially a dark and shadowy counterpart of the Crystal Arch you've been fighting him in, but without Healing Wells. Here, you will need to fight two major enemies.
 * Slash: A rapid melee strike with Diablo's hoof, claw, armblade or tail, dealing average Physical damage.
 * Fireball: A ground-based missile that, upon reaching any target or obstacle, explodes into a pool of fire, doing high Fire damage over time if you're caught in it.
 * Flame Circle (similar to Diablo II equivalent): Creates a circle of ground-based fireballs, each doing average Fire damage, moving in all directions. These do not leave a pool of fire.
 * Fire Wall: Creates a fast-moving wall of fireballs, similar to Flame Circle, but with an arc and moving faster and further. Deals same damage as Flame Circle.
 * Bone Prison: Creates a series of black pools on the ground, trying to create them as close to the player as possible. If caught in it, Diablo will teleport to you, grab you by the throat and drain your health before slamming you into the floor. This attack cannot actually kill a hero (reducing to 1 Life instead), but is often followed by a Slash. Some defensive abilities can be used while grabbed. Note that Bone Prison stuns the character instead of immobilizing them, so ing out will not be possible.
 * Teleport: Used both to get closer to ranged characters and to avoid melee combat. Used automatically if player gets caught into the Bone Prison.
 * Shadow of Diablo: Has roughly half the total health of Diablo in phase 1, uses all the same tactics of Diablo during the first phase and should be fought the same way. However, from time to time he disappears, spawning a number of Shadow Clones equal to the number of players ingame. After 30 seconds or once the Shadow Clone is dead, Shadow of Diablo will return.
 * Prime Evil's Curse: Places one of the seven curses on you for 12 seconds, which are various debuffs. For example, Baal's curse deals damage over time, Diablo's curse greatly reduces healing received, and Mephisto's curse increases both damage taken and damage done.
 * Shadow Clone: Appears at the beginning of the fight, and either every 45 seconds or after the Shadow of Diablo loses a third of its total health. The Shadow Clone takes the form of your primary class (one clone per player) and uses many of your abilities, not necessarily those you have active at a time. These abilities deal considerable damage, plus any special effects they might have, usually without Runes, and Shadow Clones have average health, so killing them as soon as possible is advised. Upon death, each Shadow Clone drops a guaranteed Health Globe.

This Wretched Light Must Be Eradicated: Once you defeat the Shadow of Diablo and escape the Realm of Terror, Diablo heals back to at least 65% and becomes more aggressive with his teleports and attacks. He also gains two more abilities:


 * Dash: Greatly increases Diablo's movement speed for a short time, making it very hard to run away from him.
 * Red Lightning Hose: identical to Diablo II ability, charged up for 1.5 seconds, and then unleashed in the same direction as Diablo is facing (slightly adjustable to keep track on the target), deals very high Fire or Lightning damage (to which you are more vulnerable to) if you get caught in the beam. If players lack the necessary protections to continue fighting through the attack, they can avoid the attack by either taking cover behind one of the two heavenly crystals in the Arch, or by outrunning it.

Continue whittling away at his health and avoiding his attacks until his lifebar is down to around 5% of his total HP, at which point the "Destroy Diablo" objective appears. At this point, the battle is won: you can hit him with everything you wish (the goal is to bring him to 1%), or just deal a bit more damage and then stand and watch. After some time, Diablo's body will explode, and his corpse collapses to the ground. After a short cutscene, the fight is over, and loot is dropped.

Uber Appearance (Soul of Evil)
Though Diablo never made it onto the level 60 variant of the Infernal Machine event, he does make an appearance for the Reaper of Souls variant of the same event as Soul of Evil, Unstoppable Hatred. Players can fight him in the Realm of Fright, taking on his appearance from the second phase of his canon encounter.

For the most part, he possesses the same attack list as that of the canon appearance, but there have been changes to his abilities: Once the Soul of Evil and its servants all die (no matter in which order), the last defeated boss has a chance to drop the Heart of Evil. This organ is needed if the hero wishes to craft a Hellfire Ring or a Hellfire Amulet, and has the same drop rate as other organs (up to 100% at Torment VI, up to 3 at once at Torment X).
 * Illusionist: Works much like the monster trait of the same name, only the Soul of Evil will make two copies of himself, rather than four.
 * Summoning: After player(s) deal 25% of the Soul of Evil's total Life, he will perform a ground stomp, stunning every hero in the arena, and summon a randomly chosen Uber boss from the other Uber locations to aid him. Once the Soul of Evil has been damaged to 50% of his total Life, he will perform another stunning stomp, then summon yet another Uber boss (not necessarily the first boss's partner).
 * Lightning Breath: always targets the closest enemy.
 * Bone Cage: causes damage to the captured character.
 * Curses: applied with melee attacks:
 * Curse of Anguish: increases damage taken and reduces healing taken.
 * Curse of Hatred: increases damage taken and damage done.

The Soul of Evil has a chance upon death to drop Star Pauldrons.

Quotes

 * "You are all deceived, my brothers. A new age has already begun. Can you not sense them? Ugly creatures born in shadow. They feel terror, hatred, and the desire to destroy. Yes, but they are not ours yet. They will open their world to us very soon, an invitation we cannot refuse. (The Discovery of Sanctuary, part 3)
 * "I LIVE!" (First words after possessing Leah)
 * "But I am more than I once was. The Seven Evils are one within me. I am the Prime Evil! Well done, faithful Adria. Go now, until I call upon you again."
 * "Now, at last, to my true goal, the one that has always eluded me - the utter destruction of the High Heavens!"
 * "Even in the heart of Heaven, angels can still feel fear." (spoken through Leah his daughter)
 * "Our long war ends today, Imperius!" (upon revealing his true form and confronting Imperius)
 * "Take one last look at your shining Heaven, Imperius. For soon, nothing of it shall remain but my laughter." (before destroying the Diamond Gate with a roar)
 * "Gaze upon the destruction I have wrought. It'll be the last thing you see. Iskatu, destroy the nephalem!"
 * "Every moment I delay you, I draw closer to my ultimate victory!" (upon the defeat of Iskatu)
 * "Rakanoth, the Lord of Despair, keeps Auriel, the Archangel of Hope, imprisoned. The Heavens are lost without her" (If the player does not press the spacebar fast enough after having killed Iskatu, it will not be heard at all)
 * "You will find no comfort here!" (If the player does not press the spacebar twice fast enough after having killed Iskatu, it will not be heard at all)
 * "Rakanoth, do not fail me, or your fate will be the same as Iskatu's and my brothers'!" (removed?)
 * "My armies flow through the Hell Rifts. Heaven will be destroyed long before you set one foot into the Silver Spire!" (upon the defeat of Rakanoth)
 * "Look upon these gardens, now they seethe with the corruption of Hell!" (upon revealing the first Hell Rift)
 * "Where is Tyrael? Fallen. Broken. He knows the truth now; I will be victorious!" (Only if the hero starts to make progress on the right path before having found the first rift)
 * "So, you approach the Oculus with the aim to destroy it? You will not succeed!"
 * "If you destroy the Oculus, my hell rift will consume you!"
 * "You think to destroy the Rift Oculus? My fiends will tear you apart!"
 * "That is not the only hell rift. The flow of my legions will not stop." (upon destroying the first rift and returning to Heaven)
 * "I draw closer to victory, Nephalem. You are too late, just as you always have been!" (upon revealing the second Hell Rift)
 * "The hell rifts are closed, but it is of no matter. Soon there will be nothing left of these High Heavens. All creation will be the Realm of Terror!" (upon destroying both Hell Rifts and returning to Heaven)
 * "Look, Tyrael - your old lieutenant."
 * "Look beneath you and see the ruin of Heaven!" (after defeating Izual)
 * "The Seven Evils are one within me! I am Legion!" (as the final battle begins)
 * "Enough! Let us see how you fare in my Realm of Terror." (as Diablo begins the second phase)
 * "Only by defeating us can you return to your own realm, but none have ever crawled from the depths of their own terror!" (as the second phase begins)
 * "You shall never wake from this nightmare." (in combat in the Realm of Terror)
 * "How tastes your fear, Nephalem?" (in combat in the Realm of Terror)
 * "You cannot defeat your own terror!" (in combat in the Realm of Terror)
 * "Can you feel your death approaching?!" (in combat in the Realm of Terror)
 * "Your Nephalem power will not help you in this realm, mortal!" (in combat in the Realm of Terror)
 * "How does it feel, knowing you have failed those who depended on you?" (in combat in the Realm of Terror)
 * "NO! This wretched light must be eradicated! All that you have known - all that you have ever loved - shall die along with you, Nephalem!" (as the final phase begins)
 * "I have a surprise for you." (BlizzCon 2017 demo)
 * "You will not find victory so easy." (BlizzCon 2017 demo)
 * "My fiends will tear you apart." (BlizzCon 2017 demo)
 * ''"Feel familiar, nephalem? You have been here before in your nightmares."' (BlizzCon 2017 demo)