Terraria One Block: How to Play the One Block Challenge (Mod, Calamity and Tips)

Terraria One Block isn't a world seed. It's a tModLoader mod called Terraria: One Block Challenge, made by Jabon. You spawn on one block, and the moment you mine it, another block takes its place. Each progression tier adds more blocks to the pool. That's the whole game.

To play it you need Terraria on Steam, the free tModLoader app, and the mod itself, from the Steam Workshop or tModLoader's Mod Browser. It's PC only. Details below.

Is there a Terraria One Block seed?

No. There's no seed code that gives you a one-block start, and I wouldn't trust a video or site that hands you one. If you've seen a "Terraria one block map" download advertised, skip it too. The mod is the way to do this.

The closest thing in vanilla is the Skyblock seed, which arrived with Terraria 1.4.5 in January 2026. You spawn on a small sky island and build outward by killing slimes. It's related, but it's not one block. My Terraria skyblock seed guide covers it, and if you're browsing seeds in general, there are the best Terraria seeds and the secret seeds too.

What the One Block mod does

The Workshop page describes it as recreating the Minecraft mod of the same name. If you know that one, it's the same idea moved into Terraria. (Never played it? One Block in Minecraft explained covers how the Minecraft version works.)

What you can get from that block depends on how far you've pushed the game. Going by the author's own description:

• Pre-Hardmode: basic ores, basic biome tiles, clouds, diamonds and wood.
• After Brain of Cthulhu or Eater of Worlds: evil blocks, hellstone, ash, obsidian and meteorite join the pool.
• After Skeletron: dungeon bricks.
• Hardmode: the early Hardmode ores and pearlstone. Chlorophyte comes after the Mechanical Bosses, lihzahrd bricks after Golem, and luminite after Moon Lord.

So bosses aren't just bosses here. They're how you unlock new materials. There are configs for changing how common each tile is and adding your own, and the author added a way to get crates through Crate Tokens in a later update.

The Workshop page was last updated on October 22, 2024 (v1.2.2) and is tagged for tModLoader 1.4.3 and 1.4.4. Terraria has had a big update since, so check the Workshop page for current support before you build a whole run around it.

How to install Terraria One Block

1. Own Terraria on Steam. tModLoader needs it.
2. Install tModLoader. It's a free, separate app on Steam for Windows, Mac and Linux. It runs as its own game with its own save folder, so your vanilla worlds stay put.
3. Get the mod. Either open the Mod Browser in tModLoader and search for the One Block mod, or find Terraria: One Block Challenge on the Steam Workshop and hit Subscribe. Steam sometimes wants a relaunch of the game before the download shows up.
4. Enable it. Go to Mods in tModLoader, switch the mod on and reload.
5. Make a new world. Spawn, look down, and mine your block.

Grab the helpers the author recommends too: Boss Checklist, Recipe Browser and Quality of Life Compendium. You'll use Recipe Browser constantly.

Playing with friends

Everybody has to run tModLoader with the same mod list. Vanilla players can't join a tModLoader game. The author said multiplayer was "hopefully" fixed in an early update, so don't be shocked if co-op has rough edges.

Can you play it on mobile or console?

No. tModLoader is a PC thing, and the PlayStation, Xbox, Switch, iOS and Android versions of Terraria don't support it. You'll see unofficial phone ports around, but they don't come from Re-Logic or the tModLoader team, and I'd steer clear. If you're not on PC, you can't play this one. More on what runs where in is Terraria cross-platform.

Terraria One Block with Calamity

The mod page lists its content-mod support as Calamity: Complete, Catalyst: Complete, Thorium: Complete, and Spirit: work in progress (the author warns it crashes on world creation, so enable Spirit after you've made a world). So if you came here for Calamity One Block, you're covered.

A few Calamity touches from the changelog: Providence drops the Blossom Pickaxe, Infernal Suevite and Brimstone Slag show up in the block pool after the Wall of Flesh, and there's an Astral Grass Seeds recipe. If you want a ready-made setup, there's a community Calamity One Block collection on the Workshop. It's not official, and it bundles more than its title says, so look through the list before you subscribe.

Don't assume other big mods play nicely with it. The author only lists the four above.

Early-game tips

• Wood and basics first. The first tier hands you wood, basic ores and biome tiles. Get a workstation and a small base going before you chase bosses.
• Use Recipe Browser. Filter it to the One Block mod to see what it adds. Players on the Workshop page report that this is how you find the Skeletron summon, a doll you craft. "How do I summon Skeletron?" is a question that keeps coming up there.
• Brain of Cthulhu. Players say the remote from Quality of Life Compendium can summon it, which helps, because getting a crimson or demon altar is another thing people get stuck on.
• Follow the boss order. Eye of Cthulhu, then Brain or Eater, then Skeletron and so on. The block pool only grows when you beat Brain or Eater, Skeletron, the Mechanical Bosses, Golem and Moon Lord, or enter Hardmode, so those fights are your real progress bar.
• Check the starting inventory. Ash Grass Seeds come with you as of v1.2.2, and there are recipes for all the grass seeds.
• Tweak the configs. If a tier feels like a grind, change tile weights instead of quitting.

Done with the mod and want more of that Terraria feeling? Try my list of games like Terraria.