Battle.net in Diablo II was never meant to be only about quest games. Blizzard North had planned three parallel entry points: Quests, Arena and Guild Halls. The Arena came with its own maps, character templates, scoring rules and several match types — a complete standalone PvP / PvPvE mode, far more elaborate than players arranging a duel out in the wilderness.

In November 1999 Bill Roper had already confirmed that the Arena would not ship with the game, while keeping the door open for a patch or a future title:

"The concept of arena combat already exists in Diablo II, since players can always turn swords or spells on each other whenever both sides agree. While we won't be adding a dedicated place for that kind of play in the retail version, we may add 'arenas' to the game world in a patch or a future game."

In the end it never came back. Still, the pre-release game data and the press visits to Blizzard North from those years are enough to sketch the rough outline of the mode.

The source material comes from these two articles, which contain a large amount of raw documentation.

Battle.net Village, Guilds, Arenas — Documentation 1

Battle.net Village, Guilds, Arenas — Documentation 2

Two Arena maps

Two arena maps survive in the game data, named DM2 and DM3. DM stands for death match.

DM2

A small tomb area. Narrow corridors and tight corners above and below, with a larger open space in the middle where pillars and walls break line of sight and let you kite.

The map objects include a personal stash, a guild vault, battle banners, and… water vapour?

That happens because the arena map is technically an Act VI map, so the game tries to read Act VI object data. The retail build has no Act VI object table, so Act V objects were substituted and one of them came through as water vapour.

Read as an Act II map instead, it fills up with portals, tunnel entrances and torches.

Neither version can represent the original design.

The Act VI object table is probably unrecoverable, so we have no way of knowing what the Arena was actually supposed to contain.

There are also a great many town entry points, which normally mark where a character appears on entering a map — in all likelihood the spawn and respawn positions.

DM3

DM3 is a large open area. Judging by how symmetric and evenly spaced its town entry points are, our guess about what those points do should be correct.

This is what it looks like when read as an Act II map. All the teleporting is amusing, but don't treat it as canon — a lone torch sitting in the lower-left corner clearly has no reason to be there.

Deathmatch scoring table

Beyond the two maps there are some numeric settings as well. One of them is the deathmatch scoring table.

In code terms, the routine that awards score to characters still exists in the game.

Character templates

Level 3 templates

Level 9 templates

Other parameters:

Mana regeneration bonus = 0

Character movement speed = 100

Attack speed = 100

Other speeds = 100

A visibly unfinished table. What it does establish is that character templates existed: you could pick an archetype outright, allocate its points, and enter a fair match with a fixed character and fixed gear.

Game creation options

Putting the pieces together, the Arena's game-creation parameters were roughly:

Match type: Deathmatch / ...

Character source: your own character / template character

Template level: Level 3 / Level 9

Template: 1–15

Difficulty: Normal / Nightmare / Hell

Hardcore: on / off

Expansion: on / off

Ladder: on / off

Which leads us to expect a public player ranking board in game, arenas that can contain monsters (a PvPvE mode), and party invites plus hostile toggling before a match begins.

On the historical side, the press trip to Blizzard North that diabloii.net made back then left behind a great deal of valuable information.

Diablo II's Battle.net has three game options: Quests, Arena and Guild Halls.

Choosing the Arena option takes you to a menu listing the currently public games for you to pick from, and you can also enter a name and password for a private game. Before entering the arena you see an options screen covering arena type, map, and character options (how many players are allowed, which classes are allowed, which character levels, and so on).

We believe there will be both ladder duels and ordinary duels.

Optional duel settings: map, map size, time of day, monster spawning, randomly placed mana or health potions, random starting positions, variable mana regeneration rate

Pre-battle wager option: each participant can stake an item both sides have agreed on; the winner takes back their own item and receives the loser's stake. Dying does not drop your gold or equipment.

Several game types were planned:

King of the Hill — requires some kind of terrain feature on the map, most likely a hill; perhaps after a set time the player standing at the very top is the winner.

Highlander — a free-for-all where everyone starts at once, each dead player leaves the game, and the last one standing wins and takes the prize (if people placed wagers). Tactics include avoiding large battles so you don't die early. Some sneaky types will hide until almost everyone else is dead, then pounce to land the final blow and take the money.

Free For All — an ongoing game: you join and fight whoever else is in it. There will probably be automatic respawns, either at random locations or in a safe area. Games of this kind may be running on Battle.net all day, possibly with class or level restrictions to join, such as "Barbarians only, character level 20-25".

Capture the Flag — some kind of team flag-capturing game. Very cool for guilds.

Siege — this needs some kind of custom map. Some players hold a defensible position while others try to break in and kill them, or perhaps simply breaking through the defences counts as a win. Archers on a tower, that sort of thing.