Mithrix

Mithrix is the final boss of the game, encountered at the apex of Commencement, the moon of Petrichor V and final stage of Risk of Rain 2.

Description
Mithrix is an ancient, cyclopian humanoid with godlike powers, much of which he shared with his brother Providence. The growing philosophical opposition each sibling had for one another worsened to the point that Mithrix was banished to the shattered pieces of Commencement, while Providence took to carrying out his vision on the world below.

By the events of Risk of Rain 2, Providence had been slain yet Mithrix's confinement upon Commencement as the King of Nothing continued. It would be the Survivors of the UES Safe Travels who reached the moon via the Celestial Teleporter to put an apparent end to him.

The deeper details and circumstances of Mithrix and Providence's relationship is detailed throughout many of the game's logs, most of which are taken from Mithrix's perspective, including those for, A Moment, Fractured, Bulwark's Ambry and more.

Adaptive Armor
During phases 1 and 3 of the fight, Mithrix has the Adaptive Armor passive which protects him against bursts of damage. Every time Mithrix takes damage, he will gain temporary armor equal to 3000 * (damage / maxHP), in other words, 30 armor per % of his max HP dealt. This temporary armor caps at 400 and decays at a rate of 40/s.

Phase 1
Mithrix will start by doing his basic attacks, which consist of running around, dashing while swiping with his hammer for 200% damage, smashing the ground with his hammer causing an explosion for 1200% damage (with damage falloff) and an additional 1200% damage on a direct hit (the hitbox is fairly small), and running at the player while firing up to 12 needles for 60% damage each. He can also jump into the air of the center of the stage and slam down, causing a 360 shock-wave around the stage which deals 400% damage. Also decrease movement speed by 50-80% if hit by the shock wave. The wave ends when it reaches the thin line made of rocks between the platform where he is first seen.

Phase 2
Terrain changes (several stone pillars rise up) and several, , and are summoned which must be defeated. Mithrix is not present during this phase while new chimeras are occasionally summoned.

Phase 3
Mithrix comes back with more powerful and different attacks, occasionally summoning Lunar Chimera Golems and, more rarely, Lunar Chimera Wisps. His moveset is similar to the first phase but the attacks have additional effects to them. He also gets more aggressive and attacks more often. His slam leaves a lingering pillar of flames that deals 150% damage per tick and sends 3 small, directional shockwaves similar to the shockwaves from the ground pound attack, dealing 200% damage and applying. Mithrix also gains an additional attack, in which he will summon moving lines of flame that spin around him and explode after short delay, dealing 900% damage and applying Crippled. This attack is repeated 4 times.

Phase 4
Mithrix steals all players' items and gains their buffs. Damaging him will release the items, one by one in the order they were obtained. In multiplayer, the items will be returned to players in round robin order, by player slot. He will fire a burst of projectiles similar to those fired by using, slowly stomping around the battlefield. He will also occasionally kneel and fire fast travelling orbs for 400% damage in eight directions, simultaneously dealing 8% of his current health in damage to himself. Also if the player has, then will spawn and help the player during the fight. Hitting Mithrix with high damage in this phase will cause him to enter a stagger state. Sometimes Mitrix doesn't take any items and simply skip this phase(this happened only late in game).

Aftermath
Once Mithrix is defeated all taken items are returned, the Moon will begin a detonation sequence with an on-screen countdown. In order to exit Mithrix's arena, the surviving players need to jump into one of the floating portals in order to teleport out. The surviving players have 3 minutes to get to the Rescue Ship and complete its holdout event in order to escape. The Event requires the players to protect the Ship by staying near it for 1 minute. Lines of flames will appear, similar to the columns used by some of Mithrix' attacks. and will spawn and attack the player but they won't enter the protection zone of the Rescue Ship.

Successfully making it to the shuttle will complete the Washed Away challenge and unlock the as a playable Survivor, and, on  difficulty, will complete the The Calm challenge and unlock.

Tips

 * Mithrix cannot climb the pillars that appear on phase 2, so if you manage to climb them and do only ranged attacks, the third and fourth phases will be very easy. The ranged attack on phases 3 and 4 can be easily dodged from higher ground too.
 * Mithrix will take but not use any, or  during phase 4.
 * Mithrix will not take during phase 4.
 * Mithrix will take and use the Captain's as well as any  during phase 4, making the fight significantly harder until they are recovered.
 * Mithrix will take and use during phase 4. However, you will regain an unspent Dio's Best Friend along with all other stolen items upon Mithrix's first death. If you take it back before he dies, he won't gain a second life.
 * and skills are capable of freezing Mithrix, unlike other bosses.
 * can use to avoid the entirety of mithrix's first phase
 * When using, two Mithrix will spawn. Players must kill both bosses before they will advance from one phase to the next. However, when one's health is emptied, it will be incapacitated until the next phase.
 * Mithrix steals items from minions, like Turrets; however he doesn't use them.
 * During phase 4, Mithrix will not use his orb attack while his health is above a certain threshold.
 * If the player has any Fuel Cells before Phase 4, additional equipment charges this item provides will remain. This may be used to finish the boss with Disposable Missile Launcher, Preon Accumulator, Royal Capacitor, etc, right after the healthbar appears.
 * On kill items such as Topaz Brooch or Will-o'-the-wisp are almost useless for Mithrix as they require an ally or player to be killed

Dialogue
Mithrix is unique in that he speaks throughout his fight, with his quotes appearing in the chat box. His dialogue may change depending on what items the player may be holding or which character they are playing as.

Toggle Dialogue Spawning


 * Pray.
 * Beg.
 * Die.
 * Be slaughtered.

Spawning (when the Player is the Heretic)


 * Regret this journey, Heretic.
 * Die again, Heretic.

Dealing damage (early phases)


 * Bleed.
 * Now is the time for fear.
 * Weak.
 * Frail - and soft.
 * You are nothing.
 * Mistake.
 * Scream, vermin.
 * Break beneath me.
 * Slow.
 * Your body will shatter.

Dealing damage (late phases)


 * BLEED.
 * SCREAM.
 * WHERE'S YOUR INFLUENCE?
 * FLEETING STRENGTH.
 * FRAIL.
 * BREAK.
 * FALSE STRENGTH.
 * DRAIN.
 * DIE, VERMIN.
 * WEAK, WITHOUT YOUR BAUBLES AND TRINKETS.

Player is killed (early phases)


 * Return to dirt.
 * Submit, vermin.
 * Die, vermin.
 * Die, weakling.
 * Become memories.

Player is killed (late phases)


 * DIE.
 * WEAK.
 * USELESS.
 * AS I THOUGHT...
 * VERMIN.

Player is killed as Heretic (early phases)


 * Return to pieces, Heretic.
 * Die again, Heretic.

Player is killed as Heretic (late phases)


 * RETURN TO PIECES, HERETIC.
 * DIE AGAIN, HERETIC.

The Player has Halcyon Seed (final phase)


 * THE GUARDIAN...? IMPOSSIBLE...!
 * THE WRETCHED GUARDIAN!

The Player has Halcyon Seed and Aurelionite is killed


 * YOU CANNOT DEFY ME, GUARDIAN
 * RETURN TO DIRT, GUARDIAN.

The Player has Halcyon Seed and is also the Heretic (final phase)


 * THE HERETIC? THE GUARDIAN? HOW? WHO PULLS YOUR STRINGS, VERMIN?

Mithrix kills a drone


 * Inferior construct. Broken.

Mithrix is killed


 * NO... NOT NOW...
 * WHY... WHY NOW...?
 * NO... NO...!
 * BROTHER... HELP ME...!
 * THIS PLANE GROWS DARK... BROTHER... I CANNOT SEE YOU... WHERE ARE YOU...?
 * BROTHER... PERHAPS... WE WILL GET IT RIGHT... NEXT TIME...