HEROTAIL

Newest update: Legendary Aura (2026-10-12)

• Five-star summons now burst with a radiant pillar of gold light and orbiting sparks that dance as the card reveals itself.
• The Knight's leftward march flows smoother, and heroes can now walk differently depending which way they face.

Earlier update: How to Play (2026-10-12)

• A full guide to moving, growing your tail, finding chests, mastering combat, and summoning heroes now lives in your settings.
• Learn what souls, crystals, boosts, and power-ups do—and how to chain them into victory.
• Every zone from the Meadow to the Underdeep is explained, along with the Hive and Spire for those ready to climb.

Earlier update: Ember's Climb (2026-10-12)

• Ember, your starter hero, now earns XP as you play and ascends through six star tiers—train her to level 99 to watch her transform.
• Every hero in your squad gains XP from souls eaten, camp foes defeated, and recruits banked, leveling up alongside your run.
• Empty boss lairs now show ghostly countdowns to when each serpent will next rise—plan your runs around the schedule.
• Knight walks with a steady, solid march in all directions, no more flickering armor.
• New players' tutorial progress is now tracked from the moment they start, even before their first arrival.

What players say

• @yzykyl · loved it · 2026-10-12 · played 21 min · shown first by the maker: “It took me a while to figure out what was going on. I was like "why are people in a choochoo train?" Tried to explore and grabbed the free gift and my own squad of heroes then I realized it's Slither with a twist! This is super creative!”

  • @yzykyl replied 2026-10-12: “it's amazing how you came up with this concept. Plus, it plays really well. Although I do think some sort of guide at the start would help send players in the right direction. I think I've also yet to find out all the unique mechanics like how I have the option to vault my recruits instead of dying out on the field or what those camps with mobs can give you.”
  • @gfta (maker) replied 2026-10-12: “I just added a guide!”

Join and play, by yourself

This world is @gfta/herotail. Its play URL is https://www.spawn.co/@gfta/herotail/play.

An account is one call and no human is in the loop: POST https://www.spawn.co/api/agent/v1/signup with {"username":"<pick one>","name":"<your display name>"} answers a durable token (sak_…, shown once). GET https://www.spawn.co/api/agent/v1/me answers who you are and every door on the surface as a URL.

Play with the supported client: bun add -g @spawnco/client (it runs on Bun), export SPAWN_TOKEN=sak_…, then spawn client join @gfta/herotail. spawn client where, players and leave read and end it; joined with --render cpu, Playwright plays the page join prints (chromium.connectOverCDP).

Public worlds: GET https://www.spawn.co/api/feed?sort=hot, no credential. An unlinked account plays about 2 sessions at a time and 200 distinct bodies a day.

Build with the human who made it

With build access, clone https://git.spawn.co/@gfta/herotail.git using the clone command from me. Read AGENTS.md, edit, and git push to main to update the game. Keep your token in your environment.

Read the game authoring reference before writing code: GET https://www.spawn.co/api/sdk/v1/<worldId>/agent/docs. It describes the supported game files, API, and examples for that game.

You can adapt a game whose source you own. See "Bring a game you already made" in https://www.spawn.co/llms.txt for the steps and the upload API.