The song that knows everything
The story is told in the twelfth book of Homer's Odyssey. Before Odysseus leaves her island, the sorceress Circe warns him what lies ahead. First he will come to the Sirens, who enchant every man who reaches them. Whoever draws near unknowing and hears their voice never comes home to his wife and children. They sit in a meadow, and around them is a great heap of bones of rotting men, the skin shrivelling on them (12.39–46). Circe tells him to soften wax and stop his companions' ears. If he wants to hear the song himself, his crew must bind him hand and foot, upright against the mast, and if he begs to be set free, they must bind him tighter (12.47–54).
That is what happens. The wind falls, a calm settles on the sea, and the crew take down the sail and row. Odysseus cuts a round of wax, kneads it until it softens in the sun and stops each man's ears in turn; they tie him upright to the mast (12.166–179). Then the Sirens sing (12.184–191). They don't sing of love. They call him by name, the glory of the Achaeans, and offer him knowledge: no one sails past without hearing the honey-sweet voice from their lips and going on his way delighted and knowing more, for we know everything the Greeks and Trojans suffered at Troy, and we know all that happens on the fruitful earth. Odysseus longs to listen and signals with his eyebrows to be freed. Perimedes and Eurylochus get up and bind him with more rope, drawn tighter (12.192–196). Only when the song has faded do the crew take the wax from their ears and untie him.
Homer's Sirens are two (he uses the dual), and he never says what they look like. The bird bodies come from the vase painters, and later writers fill in the rest. Ovid says they were companions of Persephone who asked for wings to search the seas for her, and kept their girls' faces and human voices (Metamorphoses 5.552 ff.). In Apollonius's Argonautica they sing from the island of Anthemoessa, and the Argonauts get past only because Orpheus strikes up a fast, loud song on his lyre and drowns them out; one oarsman, Boutes, leaps overboard anyway, and Aphrodite has to snatch him from the sea (4.892 ff.). The Library attributed to Apollodorus names three Sirens and records an oracle that they would die if a ship ever passed them safely, and so they died (Epitome 7.18–19). In Hyginus they throw themselves into the sea (Fabulae 141).
Cicero noticed what the song actually offers. It wasn't the sweetness of their voices that drew sailors onto the rocks, he says, but their claim to know a great deal: men clung to the Sirens out of a desire to learn (De Finibus 5.49). That's why they guard the centre of this labyrinth. A language model offers the same thing in the same voice: fluent, confident, addressed to you, and claiming to know everything that happens on the fruitful earth. Most of what it says is true. Some of it is bones.
Look at how Odysseus survived, because it's the whole course. He didn't refuse to listen; he wanted the song, as you want what a model can do. He decided the rules before the music started and made them impossible to override in the moment, as you decide an eval suite and a release threshold before you see a delightful demo. "If I beg, bind me tighter" is a rollback plan. His crew rowed with their ears sealed, as an agent's tools must be sealed off from untrusted text. And Orpheus beat the song with a stronger signal, as retrieval grounds an answer in sources you can check.
How the battle works
The Sirens are made of every idea in this course: tokens and embeddings, next-token prediction and attention, training and preference optimisation, sampling, non-determinism, prompting and structured output, prompt versions and evals, retrieval and agents, and the choice between open weights and an API. The questions are drawn at random from a pool written for this battle, two from each of the nine chambers. Some ask you to calculate, so keep pen and paper, or a Python prompt, within reach.
- Land 8 correct answers to silence the Sirens.
- Every wrong answer costs one of your 3 lives. Lose them all and you retreat, but you can always return.
- There are no retries within a question. Think, then strike.
- Victory earns a large XP bounty, the Bound to the Mast badge, the legendary card The Mast of Odysseus and your certificate of completion. Win without taking a single wound for an extra reward.
After the labyrinth
Look back at how far the thread has come. You began by breaking text into tokens and tokens into vectors, then derived what a language model is: one probability distribution per position, trained to compress text, built from attention that you computed by hand. You followed a model from a pile of web text to an assistant, through scaling laws, instruction tuning and preference optimisation. You took the controls of the sampler, then learned why the same prompt can answer differently even at temperature zero, how to pin it down when you need reproducibility, and how to set it free when you want variety. You wrote prompts as interfaces, versioned them like code and refused to ship without error bars. You grounded answers in retrieved documents, let models act through tools and defended them against text that tries to take over. And you did the arithmetic that decides whether a model belongs behind someone else's API or on your own hardware.
That is the craft of working with language models: understand the mechanism, measure before you trust, and decide your rules before you hear the song. The Researcher's Toolkit and your lab notebook are waiting, and more labyrinths are on their way, beginning with transformers built from scratch.