Doom Roguelike Enemy Analysis: Arena Master (0.9.9.7/0.9.9.8)

HP: 105/120/145/180/225 (100 base, plus 5*difficulty level squared)

Protection: 2

Ranged Accuracy: Special.

Melee Accuracy: +2

Ranged Damage: 15d1 Fire

Blast Radius: 1

Melee Damage: 1d3 (+6) Melee

Speed: 160%

Inventory: Nothing.

Experience: 608

Danger: N/A

Minimum floor: N/A

Maximum floor: N/A

Experience per Danger: N/A

Can open doors. Immune to Acid and Lava on the ground. 33% chance per action to spend it resurrecting a corpse within the Arena Master's sight.

Ranged attack is special: first they announce the attack, then on their next turn they spend it actually performing it, with this second action involving no accuracy check but involving a Dodge check to see if the Arena Master correctly targets Doomguy's tile.

Evasion: 10% base, +10% per tile of distance, making for a maximum of 90% evasion.

Attack chance: 50%?

Drops Arena Master's Staff when killed. This is in place of dropping a corpse.

The Arena Master is a unique enemy only ever encountered in the Chained Court, and only if you completely cleared Hell's Arena earlier in that same run. In an Angel of 100 or Archangel of 666 run, you will simply never encounter the Arena Master... which makes sense, given the Arena Master is really just an Archvile showing up early and with inferior offenses. (Though inflated HP, particularly on higher difficulties) 

As such, talking about the Arena Master really means talking about his version of the Chained Court, since its design is fixed and so his threat profile and the tactics that makes sense against him are reliably shaped by its design.

In the Arena Master's version of the Chained Court, you start inside a room with no enemies in sight, standing right on top of a Chainsaw, with 2 Berserk Packs toward the corners of the room. There's four doors out toward the corners. Not visible on arrival is that four fairly elite enemies are positioned around the outside of the room; they'll be Cacodemons on the lower two difficulties, Hell Knights on the middle difficulty, and Barons of Hell on the upper two difficulty levels.

The exits themselves are made into corridors by three streaks of Lava extending out west and east. This gets particularly nasty on the higher difficulties, since Hell Knights and especially Barons of Hell are quite prone to inflicting knockback, and so attempting to walk out through a door can easily result in being knocked onto Lava and so taking a ton of damage. As it's more or less impossible to have serious foot protection this early in a run... this is reliably dangerous.

To the east will be Former Humans. To the west will be Former Humans, with higher difficulties upgrading some of them into Former Sergeants and Former Captains. North of the starting zone has a few Power Cells up against the wall, while south has a few Shotgun Shells. Outside these, all ammo on the map comes exclusively from killing zombies. (This has the odd effect that Shotgun focus can fare very poorly on lower difficulties because of there being insufficient Former Sergeants to cover your ammo needs)

The Arena Master himself is also to the west, far enough away you usually can cut through the Cacodemons/Hell Knights/Barons of Hell surrounding the starting area and push west a bit before he gets close enough to potentially revive them. Not always, mind, and when he does wander eastward unusually quickly it can be quite bad.

Complicating this is that for some reason the Arena Master is completely silent, meaning you won't necessarily get warning that he's wandered close earlier than usual. Usually you can instead use dead zombies as your early warning system, where you kill some zombies to the west and once you see them reviving that means he's pretty close, but every once in a great while he'll wander basically directly east while the zombies wander more westerly, resulting in him jumping you with no warning at all, possibly while you're still trying to clean up the Cacodemons/Hell Knights/Barons of Hell.

The Arena Master himself is pretty clearly balanced around the expectation you picked up the Rocket Launcher and the Rockets from Hell's Arena and saved the Rockets for killing him. On lower difficulties you can get away with just Shotgunning him or using a Chaingun on him, but up on Ultraviolence his outrageous 180 HP and 2 Protection (So three Barons stitched together, yikes) means that even with having less damage than a regular Archvile he's just going to kill you way too fast. The Rocket Launcher is not only deadly, but its knockback is strong enough to send him out of view even if he's advanced a tile or two, allowing you to negate his attacks entirely. This is especially important for Scouts and Technicians, especially with 0.9.9.8 having added energy resistances to Marines, but even a Marine tends to do poorly if you just trade blows. A Marine taking 12 damage (Which is what 20% Fire resistances knocks 15 damage down to) will die in 5 hits, maybe 6 if they've got some Protection, which goes by fast when the Arena Master is getting 60% more turns than a base Speed enemy.

This aspect to his design is unfortunately a bit janky. For starters, the RNG has notable ability to simply kill a player as a result: a basic Rocket Launcher has only a roughly 74% chance to hit at line of sight, and does 6-36 damage, mostly hovering around 21 damage. You'll have 10 shots, of which you expect to miss 2-3 of those shots, for a total expected damage of 147 or 168, meaning the average outcome is to run out of ammo when he's got 33 or 12 HP remaining if you're on Ultraviolence. Below Ultraviolence, you'll only rarely run out of Rockets before he dies, but on Ultraviolence... if you get a bit lucky, awesome, you kill him with a Rocket or two remaining. If you get mildly unlucky, you run out of ammo when he has a Baron or more worth of HP remaining. If you get moderately unlucky (miss half your shots, say), well, you're probably not cutting through his remaining 80~ HP before he kills you.

This awkwardness intensifies with certain Angel Challenges. The weapon-constricting Challenges do tweak exactly what Hell's Arena offers as loot, but for example Angel of Shotgunnery giving you a Double Shotgun is a pretty dubious aid to your ability to kill the Arena Master. Angel of Berserk runs especially should generally simply skip Hell's Arena, so the Chained Court will generate in the easier form that doesn't include the Arena Master and doesn't lock Doomguy in until everything is dead. (But does include the all-important Chainsaw) Awkwardly, the Arena Master's worse offenses contribute to this point: if you have Berserker, he'll never trigger Berserk with his ranged attack, unlike regular Archviles always doing so.

Incidentally, that's another bit of jank to the whole thing. The exit from the Arena Master's version of the Chained Court is on the west side of the map, behind a wall that only goes away once literally every enemy is dead. If you do get unlucky such that the Arena Master is not feasible to kill, you can't run away. You're just stuck. In theory, you can try to bait him toward your starting area, trigger Berserk, and then Chainsaw him to death, but this risks him reviving Barons (or whatever) and is even more RNG-controlled by default, where each swing of the Chainsaw is only a 50% chance to hit. It'll only be 8-48 damage a swing, as well; you can get lucky and rip him apart in just a few swings, or you can constantly miss and/or low-roll and just get ripped apart by his own melee attacks.

So all-around, you can go into the Chained Court and have it be a perfectly reasonable decision, and then just... die, basically unavoidably. Exacerbated by points like that the Arena Master will almost never stray nearby walls, minimizing your ability to force Rocket Launcher hits on him by targeting terrain. (Manipulating him into approaching such walls isn't terribly practical) Nnnnot a fan.

Notably, the wall also has two random common Mod Packs behind it. The Chained Court is in fact normally your earliest encounter with Mod Packs, and so is pretty important for getting Mod Pack-based power going early in your run, even aside all the experience you get from sweeping the Chained Court.

This gets further exacerbated by the consideration of the Arena Master's Staff he drops, and more precisely the fact that the Vaults are designed to be really dubious to enter if you don't have the Arena Master's Staff. 0.9.9.8 technically sort of ablated this jank by introducing the House of Pain as an alternative to the Vaults, as the House of Pain is perfectly fine to enter without the Staff, but you don't get to 'peek' at future Special Levels at any point, so you can't go 'oh, I guess I'll just skip getting the Arena Master's Staff since this run rolled the House of Pain'. Anytime you skip the Staff, that's a 50% chance of having a future Special Level be functionally inaccessible. So you're really intended to always clear Hell's Arena and then clear the Arena Master's version of the Chained Court...

A more understandable bit of oddness is that the Arena Master is one of a handful of enemies that can be encountered in a standard run but not in Angel of 100 or Archangel of 666. Due to how Doom Roguelike constructs itself, he'd have to have some fairly high minimum floor, so high he wouldn't be appearing randomly in a standard run, at which point... well, what's the point? He'd just be an Archvile with bad damage but inflated HP.  Why bother?

A mildly unfortunate oddity is that he actually has a completely unique corpse sprite:

I think it's one of the nicer corpse sprites, but you'll never see it since he doesn't drop a body at all (Not even the 'bloody corpse' that regular Archviles and Nightmare Archviles drop), instead dropping his Staff. Alas.

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Next time, we cover the earliest mandatory boss, the Bruiser Brothers.

See you then.