Agunim

 is one of the two bosses of The Bullet's past. He also appears in a helicopter as the boss for the R&G Dept. In The Bullet's past he appears as the right hand of Cannon, as a skilled wizard who wishes to help him dominate the Gungeon. In the R&G Dept. he looks older, angrier, more grizzled, and is fully voice-acted.

Behavior
Agunim cannot be attacked directly. He has several attacks: After hitting him three times with the purple orb, he will be defeated and a hole in the arena will appear leading to Cannon.
 * Fires several streams of bullets shaped like lightning bolts that move erratically.
 * Fires a wide spread of randomly scattered bullets.
 * Fires a small cluster of bullets.
 * Fires a large purple orb which can be reflected using Blasphemy to damage him.
 * The second time, he will reflect the orb back twice; the third, four times.

Quotes
Introduction:

"So, it's you. The bullet... person.  The spell is almost complete.  Soon, my QuickDraw master rises.  All bullet kin will be slaves to his grandeur.  To be fired by HIS WILL!  I have learned from your undead master, but I am not his kind!  The usurper shall soon reign!  Turn back now!  Return to your chamber and rejoin the rest of your pathetic kind!  Or, do you think you can stop me?  GO AHEAD ON!"

Defeat:

"NOOOOOOoooooo... MASTERRRRRRRR"

Behavior

 * Shoots 2 columns of flame-shaped bullets, which then create fire between them.
 * Shoots many big bullets in bursts of 6.
 * Fires homing missiles.
 * Shoots streams of bullets shaped like lightning bolts, almost identically to his past fight.
 * Shoots 2 spreads of 4 big bullets.

Quotes
Agunim's encounter in the R&G Dept. is unique in that he is fully voice-acted.

Introduction:
 * "You killed my master!"
 * "You're the only one who can free me!"
 * "So you've finally jumped into my hole!"
 * "So you've finally come into my hole!"
 * "I've been aiming for this!"
 * "I'll send you to bullet hell!"
 * "I'm afraid I can't let you... kill your past."

Co-op:
 * "What is this child you have brought with you?"
 * "Your very presence insults me, child."
 * "This..."

During Battle:
 * "I'll kill you, then my past!"
 * "You bothersome insect!"
 * "Die!"
 * "Eat this!"

Damaging him:
 * "Agh!"
 * "Argh! ...Nice shot..."

Killed by him:
 * "You'll make a beautiful sacrifice..."
 * "Bested by your own slow reflexes!"
 * "Next time, try dodgerolling..."
 * "The gun is mine!"
 * "Oh~ not enough firepower it seems?"
 * "My master shall return!"

Defeating him:
 * "We will meet again!"
 * "You got all the good guns!"
 * "I got all the bad guns..."
 * "Forgive me, master!"
 * "You'll regret this..."

Trivia

 * Agunim's attacks in the Bullet's past are identical to Shadow Magician's. His Ammonomicon image and character sprite are also similar to those of the Shadow Magician, but with a change to the color palette.
 * This possibly relates to the Ammonomicon entry stating that the Shadow Magician is "controlled by an unseen master" and how Agunim is said to still exist within the Gungeon, attempting to escape. If so, the Shadow Magician could be a puppet being used by him to aid with his plan.
 * The Shadow Magician is even referred to as "shadow_agunim" in the game files.
 * Agunim is a reference to Agahnim from The Legend of Zelda: A Link to the Past.
 * The similarity to the Shadow Magician is also a reference to The Legend of Zelda: A Link to the Past, as you fight copies of Agahnim multiple times throughout the game.
 * It may also be a reference to the nightmare version of Agahnim from The Legend Of Zelda: Link's Awakening.
 * Even with the Galactic Medal of Valor, it will take three orbs to kill Agunim.
 * This is probably because the orbs are not an attack done by the player, but by Agunim himself.
 * Art from the physical Ammonomicon shows that Agunim is the Sell Creep.
 * With this in mind, it seems the R&G Dept. is the "great cell" he was imprisoned in.
 * In the boss encounter screen from the R&G Dept., it says "Cam Clarke as... Agunim". Cam Clarke is the voice actor for Liquid Snake, and the battle in the R&G Dept. is a reference to the Hind D battle in Metal Gear Solid.
 * His quotes when you defeat him are a reference to the lines Liquid Snake says in Metal Gear Solid.
 * Agunim in opening of the R&G Dept. seems to be wearing a red loincloth.
 * The phrase: "do you think you can stop me? GO AHEAD ON" could be a reference to the 1985 movie Final Justice, in which the main character, Thomas Jefferson Geronimo, says: "You think you can take me? Well then go ahead on."
 * In the "A Farewell to Arms" update trailer, Agunim's face in his helicopter appears with a spoiler censor mark.
 * As of the "A Farewell to Arms" update, according to his introductory phrase in the Bullet's past, Agunim is the only boss within the Gungeon who does not serve the Lich, and is hoping for his master to usurp the Gungeon throne and enslave all bullet kind as his minions.
 * The phrase "bested by your own slow reflexes!" is most likely a reference to a glitch where the game can't figure out what the player was killed by and the death screen says "Killed By Your own slow reflexes."
 * The phrases "You'll make a beautiful sacrifice..." and "My master shall return!", said when the player is killed by him on R&G Dept., gives the impression that Agunim will use the player to resurrect his master, Cannon.
 * This is likely a reference to The Legend of Zelda II, where, if the player dies, the game over screen states that Ganon will return, as they need Link's blood to bring their master back.

Bugs

 * Under unknown circumstances, Agunim in the R&G Department can shake rapidly.

Footage of this happening: https://www.youtube.com/watch?v=s6EJrHrHPiE