Hydra
The Lernaean Hydra was a monstrous water serpent with multiple heads - for every head severed, two more grew in its place. It was slain by Heracles as the second of his twelve labors, with help from his nephew Iolaus who cauterized each neck stump.
The Hydra, many-headed serpent of Lerna
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Core Myth
Hesiod names the Lernaean Hydra among the monstrous children of Echidna, sired by Typhon, which makes it a full sibling of Cerberus, the Chimera, and the Nemean Lion in the same brief catalogue of horrors. It made its home in the swamps near Lerna, in the Argolid, from which it ravaged the surrounding cattle and countryside. Apollodorus supplies the labor itself and gives the creature nine heads, eight of them mortal and the ninth immortal - a specific figure, not the vague "many heads" the myth is often summarized with. Heracles drove it from its den with flaming arrows, then found that smashing each head with his club only produced two more in its place, since the wound itself seemed to trigger the regrowth. He called on his nephew Iolaus, who burned the stump of each severed neck with a torch immediately after the strike, and the cauterized wounds could no longer regenerate. The one immortal head Heracles finally cut off and buried under a great rock, permanently unable to reach the surface, rather than trying to destroy something that could not be destroyed. He then dipped his arrows in the Hydra's poisonous blood, arming himself for the rest of his labors. Apollodorus records a detail that mattered enormously to how the labor was later counted: Eurystheus refused to credit this one toward the required set, ruling that Heracles had not defeated the Hydra by himself since Iolaus had done the cauterizing.
How many heads did the Hydra actually have?
Apollodorus, the source that narrates the labor in full, gives it nine heads, eight mortal and one immortal. Other ancient mythographers give very different counts, from far fewer up to as many as a hundred, so there was never a single agreed number in antiquity - the figure varies by author rather than settling on one canonical total.
Apollodorus, Library 2.5.2
Why couldn't Heracles just cut off all the Hydra's heads?
Every time he smashed or severed one head with his club, two grew back in its place, so attacking it directly only multiplied the problem. He only succeeded once his nephew Iolaus began cauterizing each neck with a burning torch immediately after Heracles struck, which sealed the wound before it could regenerate.
Apollodorus, Library 2.5.2
What happened to the Hydra's one immortal head?
Since it could not be killed like the others, Heracles cut it off anyway and buried it under an enormous rock, permanently sealing it away rather than destroying it. This solved the practical problem - the head could no longer threaten anyone from underground - without contradicting its immortality.
Apollodorus, Library 2.5.2
Why did Eurystheus refuse to count the Hydra as one of the ten labors?
He ruled that Heracles had not defeated the monster unaided, since his nephew Iolaus had done the cauterizing that made victory possible. This disqualification, along with a second one for the Augean stables, is why the traditional count of Heracles's labors ended up at twelve instead of the ten originally set.
Apollodorus, Library 2.5.2
What did Heracles do with the Hydra's blood afterward?
He dipped the tips of his arrows in it, since the blood carried the same lethal poison as the monster itself. Those poisoned arrows reappear later in his story, most significantly in the myth of his own death, where a robe treated with what was believed to be a love charm made from Hydra-poisoned blood ends up killing him.
Apollodorus, Library 2.5.2
Later Traditions
The exact head count was never fixed in antiquity. Diodorus Siculus and other later mythographers give figures ranging from far fewer than nine to as many as a hundred, treating the number less as a fact to be settled than as a way of expressing how overwhelming the creature was. The English phrase "hydra-headed" entered general use from this myth specifically to describe a problem that multiplies the moment it is attacked at only one point, which is the Hydra's defining trait rather than an incidental detail.
Lineage
See the full family tree4 recorded relations, each with the ancient line behind it.
Siblings
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Siblings through their shared parents, Typhon and Echidna, per Hesiod's catalogue of monstrous offspring.
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Hesiod names the Sphinx in the same catalogue passage as these monsters, but manuscripts disagree on the exact parent pairing behind her birth, which is why this sibling link is marked weak rather than strong.
Also Connected
1 recorded connection, each with the ancient line behind it.
Connected
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The arrows Heracles used against the centaurs during this labor were tipped with venom from the Hydra, killed in an earlier labor - the same poison that wounded Chiron and killed Pholus.
Where Accounts Differ
- head count variant
- Head count variant: Apollodorus gives nine heads; other ancient mythographers, including Diodorus Siculus, report figures from far fewer to as many as a hundred, with no single count treated as canonical.
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Mythology
Appears In
Killed By
Referenced By
Sources
- Hesiod, Theogony 313-318
- Apollodorus, Library 2.5.2
- Diodorus Siculus, Bibliotheca Historica 4.11
- Timothy Gantz, Early Greek Myth (1993)