The Lernaean hydra

the Lernaean hydra D File:Lernaean hydra new.png
HP	150
HD	30
XP	7599
Speed	10 (swim: 60%)
AC	0
EV	5
Will	120
Attack1	18 (bite: plain) per head (×27)
Resistances	rPois+
Vulnerabilities	none
Habitat	amphibious land
Intelligence	Animal
Uses	Uses nothing
Holiness	Natural
Size	Huge
Type	hydra, hydra
Flags	Unique Cold-blooded

An ancient, outsized serpent-like water beast that possesses numerous heads. The poets mention more heads than vase-painters can paint, poisonous venom coming out of its eyes, and that this hydra is a guardian of an entrance to the Underworld. What of this is true, you do not know.

Useful Info

The Lernaean hydra is a unique hydra with 27 heads (each head does up to 18 dmg - total: 486, but very strongly biased around the average of 260 or so) that appears in an alternate branch end of the Swamp. It has about twice the HP of a regular hydra, has 30 HD, and regenerates quickly.

Tips & Tricks

The danger posed by this monster is easily overstated. It IS a threat, and perhaps ranks among the more dangerous monsters in the game, but to a careful, reasonably well-prepared player, it is a lot less dangerous than first appears:

• It presents only a very modest threat to AC-based characters. AC functions best against many small attacks, and the Lerneaen Hydra is just that. A character with high AC 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 TLH quite 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 character, but still, unlikely to be an instadeath. Such characters will likely want to avoid engaging TLH in melee, or at the very least soften it up with wands and spells before hasting/quaffing a potion of might or simply 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 TLH in melee, but luckily, they are also the ones best equipped to do so. Use Swiftness, Haste, and Flight to maintain distance, even when TLH is in water, and repeatedly pelt it with your most powerful conjurations. Note that summons are somewhat limited in effectiveness against it as it tends to chew through them, being able to redirect its remaining attacks once it kills one monster.
• It also presents a threat to characters that are simply lower-level. However, there is generally little reason to explore the Swamp before you are XL 27. 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 exploring Swamp until you're more experienced, although TLH doesn't actually show up that often. Additionally, TLH only ever shows up on Swamp:5, so lower-level characters can feel free to explore the first four floors of the swamp (though there are still threats a-plenty on those upper floors).
• TLH 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 channeling to kill it in one go.
  • Its defenses are terrible. It literally has no 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 fairly easy to kite it to death, or at the very least take off half its HP before it gets in melee range.
• Lastly, unlike with normal hydras, don't expect a flaming edged weapon to be particularly effective. You're not going to kill TLH by cutting off all its heads, you're going to kill it by taking its HP to zero. Players should be careful about using non-flaming edged weapons - the extra HP TLH will get from regrowing heads can make it last considerably longer - but flaming edged weapons don't provide a whole lot of benefit. By all means, use one if you have one, but it isn't necessary: a non-edged weapon will do just fine, provided you have a reasonable amount of skill with it.