The Lernaean hydra

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the Lernaean hydra D
HP	99-200
HD	30
XP	5262
Speed	10 (swim: 60%)
AC	0
EV	5
Will	120
Attack1	18 (bite: plain)
Resistances	rPois+ rDrown
Vulnerabilities	None
Habitat	Amphibious
Intelligence	Animal
Uses	Uses nothing
Holiness	Natural
Size	Giant
Type	hydra, hydra
Flags	Cold-blooded Regenerates Unique

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. Each head can do up to 18 dmg for a total of 486, though very strongly biased around the average of 260, and reduced 27 times by AC/EV rolls. In addition, it has about twice the HP of a regular hydra, has 30 HD, and can knock down trees by simply moving through them. Other than that, it behaves exactly like a normal hydra (notably that it swims and regenerates quickly).

Lerny can occasionally be found in Swamp:4. If Swamp hasn't generated in your game, it may very rarely appear inside a specific runed door vault ("nicolae_hydra_factorization"). It can also appear as a zombie or skeleton in one ending.

Strategy

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 less dangerous than it first appears:

• Lerny is a melee-only monster that's relatively frail - despite the HP, Lerny has no AC and minimal EV, so it can be pelted by sufficiently strong ranged attacks. Even melee characters can use throwable or wands. It has no resistances except for poison, and it cannot see invisible.
• Each head checks AC/EV/SH separately, so a heavily armoured player is unlikely to die in 1-2 hits. A character with 40+ AC (generally from high Armour skill and highly enchanted armour) can expect to take on average 20-30 damage/turn from this monster. By comparison, a character with about 20 AC will take twice as much damage/turn.

Still, Learny can deal massive damage. In theory, it can 1-turn kill even a heavily armoured character. Great care should be taken to not let Lerny into melee range.

Tackling Lerny

• If Lerny is far away and clumped up with a bunch of monsters, a scroll of immolation + ranged attacks can be brutally effective. Ideally, haste and flight should be used in case something goes wrong. You can also use summons, undead, or other allies as immolation fodder for a similar effect.
• A phantom mirror can be brutally effective against Lerny. The phantom often moves first, so it's likely to kill (or severely damage) the original.
• Lerny can't see invisible, although note that if you're in water and not flying, invisibility does not work.

Swarming with allies generally doesn't work due to Lerny's ability to redirect leftover attacks. Summon Cactus Giant isn't effective either, as the spines will only affect a hydra once per turn. Sufficiently powerful allies like Malign Gateway can work, though.

Also, keep in mind that you don't have to kill every monster possible. 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.

Tips & Tricks

• Lerny is a hydra, with the usual head-cutting mechanics:
  • Flaming edged weapons do cut off heads, but going from 27 to 26 heads doesn't make a big difference. If you have a renewable/cheap means of escape, you might be able to chip away at the head count.
  • Lerny is capped at 27 heads. Non-flaming edged weapons still cause the healing, but won't increase the number of heads. While a normal edged weapon will likely prove ineffective, a weapon of freezing can at least slow Lerny down (letting you escape).
  • Lerny is much easier to fight when encountered as a zombie. On top of the usual weaknesses for derived undead, such as lowered speed and willpower, its heads will not regrow when severed, and it will not regenerate health.

Trivia

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