Voidgloom Seraph

"If Necron is the right-hand of the Wither King, this dark demigod is the left-hand."

The Voidgloom Seraph (/ˈsɛrəf/, "the burning one"; plural Seraphim /ˈsɛrəfɪm/) is a Slayer Boss in the Enderman Slayer track. It is significantly stronger than all other Slayers.

Spawning
The Voidgloom Seraph spawns as the end boss of a Enderman Slayer Quest after the required amount of Combat XP is earned by killing Enderman-type mobs. When the last required mob is killed, purple particles will appear around the location of its death, and the Voidgloom Seraph will spawn in its place after a short time.

Behavior
The Voidgloom Seraph is a Enderman-type mob hostile to all players. It has the appearance of an enderman with critical particles following it. It has a smaller aggro range compared to other Slayers.

Half the damage of all Voidgloom Seraphim is dealt as AoE damage, damaging all players fighting the Seraph.

Occasionally, it will teleport behind or to the side of the player it is attacking. This has a higher chance to occur if the player has not attacked the Seraph for a short time.

All Voidgloom Seraphim are immune to the abilities of Aspect of the Dragons and Ice Spray Wand. Like normal Endermen, they are also immune to most arrows, except those from Juju Shortbow and Terminator.

Upon spawning and upon reaching 2/3 and 1/3 health, it protects itself with a hitshield (Malevolent Hitshield). This shield has no invincibility frames but each hit drains the shield by 1 regardless of damage. All types of arrows can damage this shield. Purple particles surround the Seraph when its shield is up. Upon being destroyed, it resumes attacking as normal. The Seraph cannot take damage past 2/3 and 1/3 before entering the hitshield phase, making it impossible to use, or other methods to kill it in one hit.

is 75% less effective on all Seraphim except when the Hitshield is active.

As with all Slayer bosses, if the Voidgloom Seraph has not dealt damage to a player for some time, it will begin rapidly regenerating health. The regeneration immediately stops when it hits a player again. If 4 minutes pass without the boss being defeated, it will despawn, failing the Slayer quest. A timer is shown above its head indicating the remaining time.

Each tier has all of the abilities from the ones before it.

Malevolent Hitshield has 15 hits.

Malevolent Hitshield has 30 hits.

Upon reaching 1/2 health, the Seraph will begin to hold Yang Glyphs, which appear as a beacon. After 2 seconds, it will throw the glyph to a spot within 10 blocks. Any player fighting the Seraph can destroy the glyph by standing adjacent to or on top of it. If it is not destroyed within 5 seconds, it deals 10,000,000 damage to all players fighting the Seraph. The Mithril Coat’s ability can block this damage. Glyphs cannot be thrown when the Hitshield is up. The Seraph will continue to try to throw Glyphs until it is defeated.

Malevolent Hitshield has 60 hits. The boss gains +3,000 DPS every 3s the shield is up. Yang Glyphs begin at 2/3 health and are thrown more often.

Upon reaching 1/3 health, the Seraph will begin to spawn Nukekubi Fixation heads around the player it is attacking. The heads can be destroyed by looking at them for 0.5s; when they are destroyed, they will play a hissing sound. Each head deals base 800 DPS, which is doubled for each other head alive. Show/Hide DPS by Heads

Malevolent Hitshield has 100 hits. The boss gains DPS every 3s the shield is up. Yang Glyphs have similar behaviour. Fixations have similar behaviour but deal base 2,000 DPS. Show/Hide DPS by Heads At 5/6, 1/2 and 1/6 health, the Seraph becomes invulnerable for 8 seconds, taking the appearance of being seated. During this time, it casts 12 Broken Heart Radiation beams: 4 groups of 3 stacked 1 block on top of each other, each group at 90° to each other. The beams rotate clockwise for the duration; they begin blue and change to green over the 8 seconds. Any player fighting the Seraph who comes into contact with a beam takes 25% of their health as true damage and has their healing reduced by 12% for 90s. Yang Glyphs can be thrown in this phase.

Minibosses
These are possible Minibosses that could spawn upon killing a Enderman when a Voidgloom Seraph Slayer quest is active. It is also possible that after killing one of these minibosses, another could spawn immediately.

Trivia

 * The Voidgloom Seraph has the 2nd highest  of all non-dungeon enemies in the game, behind Dante.
 * Its name may be a reference to Seraph of the End.
 * The name of Nukekubi Fixations are a reference to nukekubi, a mythical creature in Japanese folklore whose head detaches from its body.