The Lernaean hydra

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the Lernaean hydra DThe Lernaean hydra.png
HP 99-200
HD 30
XP 5262
Speed 10 (swim: 60%)
AC 0
EV 5
Will 120
Attack1 18 (bite: plain)

Type of Meat Inedible
Resistances rPois+
Vulnerabilities None
Habitat Amphibious
Intelligence Animal
Uses Uses nothing
Holiness Natural
Size Giant
Type hydra, hydra
Flags Cold-blooded
A huge beast, mightiest of hydras, infamous in myth and legend. It flows through the water faster than a human can run, swatting aside trees as though they were matchsticks. Its many heads slaver and gnash constantly as it hunts for prey to slake its bottomless appetite.

“The second Labour which he undertook was the slaying of the Lernaian Hydra,
springing from whose single body were fashioned a hundred necks, each bearing
the head of a serpent. And when one head was cut off, the place where it was
severed put forth two others; for this reason it was considered to be
invincible, and with good reason, since the part of it which was subdued sent
forth a two-fold assistance in its place. Against a thing so difficult to
manage as this Herakles devised an ingenious scheme and commanded Iolaos to
sear with a burning brand the part which had been severed, in order to check
the flow of the blood.”
-Diodorus Siculus, _Bibliotheca Historica_. [4. 11. 5.]. c. 100.

For a list of all reptiles, see list of reptiles and amphibians.

Useful Info

The Lernaean hydra ("Lerny" for short) is a unique hydra with 27 heads that appears in one of the branch endings of the Swamp. Each head can do up to 18 dmg - total: 486, but very strongly biased around the average of 260 or so. In addition, it has about twice the HP of a regular hydra, has 30 HD, can knock down trees by simply moving through them, swims as fast as any hydra, and regenerates quickly.

Tips & Tricks

This monster is a threat, and perhaps ranks among the more dangerous monsters in the game, but to a careful, reasonably well-prepared player, it is much less dangerous than it first appears:

  • It presents only a moderate threat to characters with very high AC. AC functions best against many small attacks, and the Lernaean Hydra is just that. A character with high Armour skill wearing gold dragon armour or crystal plate armour can expect to take at most 20-30 damage/turn from this monster. Not trivial, but considering that most characters with high AC will likely also have high HP, this makes Lerny manageable.
  • To an EV-based character, it presents a threat, but still less of one than might initially appear. A character with an AC of 18 and an EV of 35 can expect to evade half its attacks, and reduce the damage from the rest by about 1/2. This translates to an average of about 60-65 damage/turn. This is definitely more of a threat than against an AC tank, but still unlikely to be instant death. Such characters will likely want to avoid engaging Lerny in melee, or at the very least soften it up with wands and spells before hasting/quaffing a potion of might or berserking to attack it.
  • It presents the greatest threat to low-HP spellcasters who have chosen not to train much in the way of defensive skills. These characters will absolutely want to avoid engaging Lerny in melee, but luckily, they are also the ones best equipped to do so. Use Haste and (careful use of) Swiftness to maintain distance, use flight to deal with the water, and repeatedly pelt it with your most powerful attack spells. Note that summons work rather poorly against it, as it is able to redirect its remaining attacks once it kills one monster and will chew through your armies with alacrity.
  • It also presents a threat to characters that are simply low-level. However, there is generally little reason to explore Swamp:4 before you've found the Vaults and need to pass the rune lock. It's not a horribly dangerous area, but it provides little in the way of loot and only modest XP for such a large branch. If you don't have a good suite of escape spells or good AC, you may want to delay going for the Swamp rune until you're more experienced, although Lerny doesn't actually show up that often.
  • Lerny has several crucial weaknesses that are easily overlooked:
    • It has no resistances other than poison. Conjurers and elementalists of all stripes will easily be able to inflict damage on it.
    • It actually has fairly low HP for such a powerful unique. Unlike nasties such as Cerebov or Antaeus, spellcasters are unlikely to need a source of MP recovery to kill it in one go.
    • Its defenses are terrible. It has literally zero AC, and its EV is negligible for all but the most inaccurate spells. As with the other weaknesses mentioned, this means that it generally doesn't take long to kill.
    • It has no ranged abilities. Thus, it is technically possible to kite it to death, or at the very least take off much of its health before it gets in melee range. Just be sure not to forget that it can plow through the Swamp's many trees, making them useless for kiting around. Lerny also swims quickly in water, which will make playing keep-away harder in the waterlogged Swamp.
    • It cannot see invisible and only has animal intelligence. Not only will Lerny have difficulty tracking you down, but you'll have an easier time dodging attacks and might even be able to get off a devastating stab.
  • Flaming edged weapons will still burn off heads like normal, but given that Lerny has 27 heads the impact is less noticeable. It will let you take it out slowly however; if you can't stand up to it for more than a few turns, you can escape, and the next time you fight it it'll have fewer heads to start with. Just make sure you have sufficient renewable means of escape that you won't be wasting too many critical resources (scrolls of blinking, potions of haste, etc.) doing so.
    • Considering Lerny is already maxed out at 27 heads, the only negative effect of attacking with an edged weapon is the health it regains when regrowing any heads you cut off. You probably won't be able to kill it with an edged weapon before it eats you, but a weapon of freezing might slow it down long enough for you to get some distance.
  • A phantom mirror could help vanquish Lerny or greatly reduce its health, but considering it is worth the equivalent of about 5 hydras, it might be wiser to just let it survive if you can still find a way to capture the rune.
  • A wand of scattershot does the job quite well with as little as 5 levels in Evocations. It's most accurate at point-blank range, but that's somewhere you generally don't want to be standing with Lerny. You can use other wands like iceblast, acid, or clouds to soften Lerny up, then use scattershot when it closes to two tiles away.
  • Keep in mind that you don't have to kill every monster possible. Sure, Lerny's worth a good chunk of experience, but if you don't have a safe way to kill it, just grab the rune and go. Alternatively, you can come back after you've explored other areas and gotten stronger, since you'll only need the Swamp's rune once you're ready to open the Realm of Zot.


The Lernaean Hydra was a monster in Greek mythology that was killed by Hercules as one of his Twelve Labors.