The Burning Arena is a Cataclysm dungeon in the Nether. It contains a miniboss, the Revenant, and the main boss, the Ignis.
How to Find the Burning Arena
The Burning Arena is a sizeable Colosseum-like structure that spawns in the Nether. The Burning Arena itself is almost one hundred blocks high, with it appearing above and below the surface. Therefore, you have a good chance of coming across it naturally when exploring the Nether.
Though you can also craft the Eye of Flame. Like an Eye of Ender, it can be used to locate the nearest Burning Arena. Only one is required, as they don’t break, and they must be used in the Nether.

To craft the Eye of Flame, surround an Eye of Ender with 3 Blaze Powder, 2 Netherite Scrap, and 3 Soul Sand. Release the eye in the Nether, but do be careful, as there is a chance they’ll fall into lava. They won’t burn but might be dangerous to retrieve.
Alternatively, you can enter some commands, provided you have cheats enabled. You can use the commands /locate cataclysm:burning_arena or /locate structure cataclysm:burning_arena if you’re on Minecraft 1.19+.
About the Burning Arena
The Burning Arena has three floors. The top contains an Altar of Fire in the center, which is used to summon the main boss, the Ignis. To invoke it, you’ll need to go down a level to the middle floor.
Two Ignited Revenants can be found here. These look like Blaze but are much more powerful. They have multiple shields that circle them, allowing them to absorb more damage and even block attacks.

Ignited Revenants have 80 Health and 12 Armor points and count as mini-bosses. When fighting them, expect them to make attacks such as Ashen Breath and the Bone Storm, where they can fire smoke toward you or launch bones at you, dealing high amounts of damage.
Killing the Ignited Revenant will provide you with Burning Ashes, which are needed for the previously mentioned Altar of Fire. To kill more Ignited Revenants in the future, you should try and find new Burning Arenas.

Back upstairs, you can use Burning Ashes on the Altar of Fire, which is in the middle of the top floor of the Burning Arena. The Burning Arena will begin to shake, and after a few seconds, the Ignis will spawn upon the Altar of Fire.
It’s one of the more challenging bosses in the Cataclysm mod. The Ignis has 450 health and 10 armor points in total. Due to the Ignis having a large Shield, some ranged attacks will be blocked, but you can still get a few hits in.

Mostly, you’ll want to bring high-healing items, as well as things that give movement speed. Ignis will follow you around the Burning Arena, and it isn’t easy to create distance. Even if you do get away from Ignis, it’s able to jump in the air towards you, knocking up terrain.
Defeating Ignis will give you some Ignitium Ingots. These can be used to create the Sword and Shield carried by Ignis. They’re called the Incinerator and the Bulwark of the Flame. You can also receive the ‘Symphony – God of Blaze’ Music Disc.