Bring Your Own Key
Play as much as you want, whenever you want, with any model.
$4.99 a month
Play Without Limits
No turn limit. You choose the model that writes your story.
No turn limit
Play as long as you like, every day.
Everything unlocked
Director Mode, custom creation, unlimited saves, your own title.
Your model
Choose who writes your Rome, one model or two.
Your settings
Scene length and memory, up to sixteen past scenes.
Get Started In Five Minutes
The Game Master runs on an AI model, and every scene it writes costs money; we pay for that, which is why turns are limited. A key is a long password from a company that runs these models. Sign up, add a little credit, look for the words API key on their site, and paste it into Legio Aeterna. From then on the writing runs on your account and the turn limit disappears.
Where To Get One
Every provider works. These are the easiest places to start.
OpenRouter
The easiest place to start. One key, hundreds of models from every company.
OpenAI
gpt-5.4-mini writes clean prose for very little. The API account is separate from ChatGPT Plus.
Anthropic
Haiku is cheap, Opus is the strongest, and Sonnet sits between them. Sonnet suits Legio well.
Anywhere else
Together, Fireworks, Groq, Mistral, DeepSeek, DeepInfra, and any service using the standard format. Type its website and the game fills in the address.
No key at all? The same plan also plays against a model running on your own computer with Ollama or LM Studio. Play on your own machine.
Pick Your Models
One writes the scenes, one handles the small work.
The first model writes every story scene; the second handles conversations, fight rounds, letters, and the Game Master's notes, where a cheap fast model does fine. Change either in Settings whenever you like, or tick one box and run everything on a single model.
Paste a key from OpenAI, Anthropic, or Google and the game lists the models that key can reach. Anywhere else, type the model's name; the catalog is linked right there in Settings. Not sure? Leave the model fields alone and the game plays on a solid default for your provider.
Try It Now
Paste your key. Change the model. Run the same line twice.
How far it strays from the likeliest next word.
How much of its vocabulary it weighs at each word.
How many candidate words it keeps in the running.
Pushes it off words it has already leaned on.
Pushes it toward subjects it has not raised yet.
The game itself answers faster than this panel: live turns stream in word by word and run through optimizations the playground skips.
Average Tokens Per Turn
What one turn sends, and what comes back.
A token is a short piece of a word, and models charge by the million of them. Your provider lists each model's price per million tokens next to it, so with the figures above you can work out a turn before you spend anything.
Most providers cache the repeated part of the input, and the Game Master's rulebook barely changes between turns. In live play that covers half or more of what a turn sends, so you rarely pay the full rate.
Your Key Stays Yours
On your device
Saved in this browser, on this device. On another device you enter it again.
Never stored
We never save it on our servers. There is nothing of yours here to lose.
In transit
It travels encrypted, through one server that passes it straight on and keeps no copy.
Yours to cancel
Delete it where you made it and it stops working everywhere, at once. Make one just for this game.
Turns are unlimited, with one limit: 400 a day, resetting at midnight. Every turn still costs us server work even when the writing runs on your key. Four hundred turns is a very long day of play.
If Something Goes Wrong
Key rejected
Check that nothing was lost in the copy and paste, then press Test key. It shows you exactly what came back.
Out of credit
Top up on their billing page. The game tells you plainly when the account runs dry.
Model not found
Model names must match their catalog exactly.
Rate limited
A brand new account is throttled for its first few days. It eases off on its own.
Any qeustions? Write to [email protected] and we will get you playing.
Every turn on your own key, $4.99 a month.