Minecraft Dungeons:Arena Battle

An arena battle, also known as an ambush for short, is a battle between mobs and heroes.

Locations
Arena battles occur in every location in the game except for. Some locations have boss ambushes which spawn minibosses. Those locations include: The Treetop Tangle is the only mission to have an ambush which spawnes a boss.
 * (Only with Echoing Void DLC)
 * (Only with Echoing Void DLC)
 * (Only with Echoing Void DLC)
 * (Only with Echoing Void DLC)
 * (Only with Echoing Void DLC)
 * (Only with Echoing Void DLC)
 * (Only with Echoing Void DLC)
 * (Only with Echoing Void DLC)
 * (Only with Echoing Void DLC)
 * (Only with Echoing Void DLC)

Behavior
Arena battles operate differently from boss fights, where arena battles spawn a lot more weaker mobs than sometimes a boss. The battle format also differs from boss fights, where it usually spawns in waves, such as the one in the Pumpkin Pastures. The battles usually start out with several weak mobs. Over time, the waves of mobs get stronger until the battle ends, or when the boss appears. No matter what, battles always spawn mobs from the mission it takes place in.

There are also similarities between arena battles and boss fights. They are both triggered by certain events like heroes entering an arena, such as the Redstone Mines battle, or by pressing a trigger, such as the bell in the Pumpkin Pastures. Some other triggers include buttons, levers, and pillars.

There is a chance for these ambushes to have mini bosses. There are nine missions where ambushes spawn two minibosses: the Woodland Mansion, the Pumpkin Pastures (Only with Echoing Void DLC), the Desert Temple (Only with Echoing Void DLC), the Basalt Deltas, the Crimson Forest, the Abyssal Monument, The Stronghold, the End Wilds and the Broken Citadel. So far, it isn't possible to have arena battles that spawn three bosses, but in the Radiant Ravine there is an arena battle that spawns four of them. Another similarity between arena battles and boss fights is that they have their own special music. They can also both be started by the Arch-Illager, the Jungle Abomination, the wretched wraith, the tempest golem, the ancient guardian and the Vengeful Heart of Ender. Each of them have their own summoning animation. The Arch-Illager teleports in, summons an ambush, and then teleports out. The jungle abomination, wretched wraith, tempest golem and ancient guardian just roar to summon an ambush, producing their own effects while doing so. The Vengeful Heart of Ender often crawls near the hero making hissing sounds to summon an ambush.

Battles are also usually announced by the game, such as boss fights. When arena battles end, they usually spawn chests that contain loot, whereas when boss fights end, their loot drops directly from the boss' corpse.

Arena music
If the player escapes the arena while the music is playing, the music continues until another ambush or a boss fight is cleared.

Mainland and Hero Pass DLCs

 * arena1 (Arena Music for the Creeper Woods, Pumpkin Pastures, Redstone Mines, Cacti Canyon, Obsidian Pinnacle, all Jungle Awakens missions, and all Creeping Winter missions)
 * arena2 (Arena Music for the Squid Coast, Desert Temple, Fiery Forge, Highblock Halls and the Underhalls)
 * Invocation (Arena Music for Woodland Mansion and Woodland Prison Ancient Hunts)
 * Menta Menardi (Arena Music for Spider Cave Ancient Hunt)

Howling Peaks

 * Summit (Arena Music for Windswept Peaks)
 * Ascension (Alternate Arena Music for Windswept Peaks)
 * Squall (Arena Music for Colossal Rampart)
 * Flurry (Alternate Arena Music for Colossal Rampart)
 * Rush (Arena Music for Gale Sanctum)
 * Scud (Arena Music for Gauntlet of Gales)

Flames of the Nether

 * Routers (Arena Music for Nether Wastes, Nether Fortress and Gold Room Ancient Hunts)
 * Metaluna (Arena Music for Warped Forest and Soul Sand Valley)
 * Torn Acinder (Arena Music for Basalt Deltas)
 * Kermetic (Arena Music for Crimson Forest)

Hidden Depths

 * Cnidoblast (Arena Music for Coral Rise)
 * Nematocyst (Alternate Arena Music for Coral Rise)
 * Truched (Arena Music for Radiant Ravine)
 * Klyka (Alternate Arena Music for Radiant Ravine)
 * Swashes (Arena Music for Abyssal Monument)
 * Pit Fight (Alternate Arena Music for Abyssal Monument)

Echoing Void

 * Drawn (Arena Music for The Stronghold)
 * Closer (Alternate Arena Music for The Stronghold)
 * Nothingness (Arena Music for End Wilds)
 * Void (Alternate Arena Music for End Wilds)
 * Shattered (Arena Music for Broken Citadel)
 * Apart (Alternate Arena Music for Broken Citadel)

The Tower

 * Tower Arena (Arena Music for The Tower)
 * Tower Boss (Arena Music for The Tower boss floors)