20 Hydras (or 1 Chaos Hydra)
You can either run this as 20 different types of hydras, or as a random table for a hypothetical Chaos Hydra that has a bunch of weird heads.
A flailsnail-headed hydra is basically just a flailsnail with head regeneration and without the weird shell effects, but if it's a hammer-headed hydra, that's pretty cool. Especially if all the heads are slamming down asynchronously.
- Bug-eyed, frog tongue. 30' ranged attack roll, target must pass a hard (-4) Str check or be pulled into the mouth for a bite attack.
- Rabid and albino. 2-in-6 chance to attack self. Will attack most wounded heads in an attempt to make more heads (which is what any smart hydra would probably do).
- Floating. Head flies off from body and flies around like a goddam flying crocodile head.
- Mosquito head shoots live stirges, which then collect blood and return via its ear.
- Featureless nozzle. Vomits piles of slippery acid, 30' cone, 1d6 damage per turn until washed off, and the acid on the ground functions like grease.
- Flailsnail flail. 2d8 damage, -4 to hit.
- Emaciated. Bites for a mere 1d4 damage when attacked, but when severed, it's skin sloughs off and it fights like a giant snake for 3 rounds (screaming) before dissolving into dust (which will also be screaming if you hold it up to your ear).
- Telekinetic. Knows telekinesis and is strong enough to pick up people and fling them against walls.
- Monocular. Antimagic cone in front of head.
- Cnidarian Hydra. Grapples like a black tentacles spell, stings for 1d6 non-lethal damage while held.
- Psychovampiric. Knows vampirokinesis (save or have all of your blood sucked out of you, which then orbits the caster in a bloody halo. The caster is paralyzed for 2 turns, and if the caster is still alive at the end of that time, the target dies from massive, postponed blood loss, and the caster heals for 2d6+2 HP.)
- Mirror-blooded, blue-skinned. Whenever this head takes damage, half of that damage is mirrored onto the attacker.
- Doppleganger. Shape-shifts its face to resemble a loved one whenever it is attacked. You must succeed on a successful Charisma check to attack a head (failure indicates hesitation). And if you actually cut off your mom's head (or whatever) you gain an insanity point. The hydra is only capable of duplicating one head each time.
- Worm. This head burrows underground and then bursts forward to attack you with only a tiny fraction of a second forewarning, then retreats. (Usually requires readied actions to hit.)
- Uterine. Launches live human infants at you like a fucking cannon. Infant has a 10% chance to survive this, and if they survive, they will age 16 years in the first 16 days, and grow up with an irrepressible urge to be dragonslayers.
- Ghidorah. This golden head shoots lightning lasers (1d6 damage, but in a straight line, save for half). The body also has wings and is capable of flying into space. It has a second lair on the moon with a second treasure hoard.
- Spiral Drill. On a hit, shield is destroyed if a save is failed. If no shield, then armor.
- Witch-Nymph. Shrieking and beautiful. On a hit, target must save vs charm person. If there are more than one of them, a pair of them can spend a turn tying a knot in one's hair and a player must immediately save or have a limb of the hydra's choice snap. A successful save indicates that the limb is wrenched and useless for 1d6 rounds.
- Hammer. Spends one turn raising itself up in the air (out of melee range) and then slams down for triple damage on the next turn.
- Rapier-tongued. Sword is sharp and straight like a fencing weapon. It gets +2 to AC against swords and will duel whichever swordsman looks most proficient, to the exclusion of all others. If there is no swordsman (or they look incompetent like NPCs) it will attack whoever looks most dangerous. The hydra is incapable of speech, but if it is insulted wittily (DM's discretion) it will get -2 to attack for a turn.
This is a normal-looking hydra except for the fact that it appears to be monstrously pregnant. When it is fighting, players can feel themselves being pulled toward it's gravid belly, and call feel the pressure of amniotic fluid on their eardrums.
When the players kill the hydra, they all die and are sucked into the hydra's womb. They then burst from the womb as an ungodly amalgam of all players (use fusion rules) with 20' necks and a bite attack for 1d6+Str. The teeth from the severed heads then grow into lizardman warriors (twice as many as players) which try to kill the player-hydra with their own weapons (looted from the bodies).
If all of the skeletons are killed, the player-hydra will split back into it's constituent selves. Also, they have a copy of their own corpses, which I've learned can be extremely useful.
That's a bit heavy handed, though, so ALTERNATIVELY this could be something like a vampiric hydra that bites people, tasting their blood, and then when the hydra dies, anyone who had their blood drank gets turned into the composite hydra. The hydra tries to taste everyone, of course.
ALTERNATIVELY, try to get player buy-in. Maybe they need to all impregnate the God Egg on level 5 of the dungeon and be reborn into a glorious new reptilian body in order to access the Plane of Reptiles. I imagine it just being like a giant, squishy egg cell. Dudes can probably just ejaculate into it, but girls might have a harder time. (The egg probably only needs a bit of blood to get going, but if you want to shove menstrual fluid in there, that'll work, too.)
This is a golem-hydra. Each head is a floating IOUN stone, about the size of your first, disconnected from the body (but incapable of getting more than 20' away). Each gemstone is unique, and while most are spherical, all heads have different characteristics. Each head is styled after the shape and pattern of a reptilian predator. For example, the "viper" head is vaguely triangular and is covered in a pattern reminiscent of snake scales.
It has a spherical body that spins around like a giant top. It is easy to track because it leaves a divot in the dust. If it needs to go up stairs, the "heads" will serve double-duty as feet. If it is killed, it shatters completely and leave 1d3 IOUN stones in the dust. All of the heads shoot beams.
If a head is shattered, the shards will fall to the ground and begin to regenerate. They have AC 10 and must take 8 damage from bludgeoning (to smash them to smithereens) and/or fire (to melt them to the floor) before the next turn, or they will regenerate into 2 new IOUN heads.
HD 2 + 2 per head AC plate Attacks (see below)
Move 12 Int 12 Mor 12
- "Viper". Magic stealing beam. Save or lose your highest level spell. The Hydra will cast that spell next turn.
- "Constrictor". Save or be caught in a psychic vice-grip: immobilized, held 6 inches off the ground, and take increasing damage each round. (1d6 the first round, 2d6 the second). Treat this psychic grip as having Str 22.
- "Frog". Teleportation to a random room in the dungeon. (I know frogs aren't reptiles but whatever.)
- "Toad". Save or become stricken with Umbral Toad venom. While so affected, you take 2d6 damage every turn you are awake, but you can fall asleep whenever you wish.
- "Caiman". 3d6 damage, and if the target fails a save, they become a magic magnet for 1 round: all spells within 40' are redirected to them as a target.
- "Dragon". Does 3d6 bite damage (this is still a beam of phantasmal dragon jaws) and the target must save vs dragon fear.
- "Stegosaur". Resonant hum. 3d6 sonic damage in a 60' line, save for half. Targets in metal armor get a penalty to their roll equal to their armor bonus to AC, because their armor functions as a resonant tube.
- "Lizard". Target takes 2d6 radiant damage for every eye that they have.
- "Ankylosaur". Target's HP is cut to half of it's current total. If they succeed on a save, it is cut to 75% of their current total.
- "Crocodile". 2d6 damage and the target must save, or their weapon turns into metal dust. (Note: this stuff is highly explosive when dispersed through the air.)
- "Komodo Dragon". 2d6 damage, then save or lose 2d6 Strength. If you fail this save, it spawns a 1 HD homunculus in an adjacent square that is loyal to you, but completely moronic.
- "Ichthyosaur". Ice beam for 3d6 damage in a line. Additionally, on the second round of combat, it will begin resonating. As long as it is resonating, the strongest player (icthyosaur's choice) is reduced to being a copy of the weakest player (icthyosaur's choice). Treat their stats and abilities as a mirror image. Everything except for the inventory list, basically. When the IOUN hydra is killed, the "weakest" player gets a bonus +1000 XP and the "strongest" player loses -1000 XP.
This is a beholder suffering from a horrible skin disease contracted from a Hydrada. It's central eye has turned into a Sphere of Annihilation, and each of it's minor eyestalks has grown into a biting hydra head. The eyes cannot fire beams any more--instead, the abilities are activated on a bite.