Hydra 5e: Stats, the Multiple Heads Rule and How to Kill One

A hydra is a CR 8 Huge monstrosity with AC 15, 172 hit points (184 in the 2024 rules) and five heads. It bites once per head every turn, at +8 for 10 damage each with 10-foot reach. Every turn in which it takes 25 or more damage, one head dies. At the end of the hydra's turn, it grows two heads for every head that died, unless it took fire damage since its last turn. Cutting heads off without fire makes the hydra stronger. Cutting them off with fire is the fastest way to kill it.

Table of Contents

• •Hydra Stat Block (2014)
• •The Hydra in the 2024 Rules
• •How the Multiple Heads Rule Works
• •How the Hydra Fights
• •Running a Hydra Encounter
• •How Players Beat a Hydra
• •Hydra Encounter Ideas
• •Frequently Asked Questions

Hydra Stat Block (2014)

This is the hydra from SRD 5.1, the same creature as the 2014 Monster Manual.

Its offense is simple: one bite per head, all at +8, 10 piercing damage each. Its defense is where the stat block gets interesting. AC 15 is low for CR 8 and its saves are poor (Intelligence -4, Charisma -2, Wisdom +0), but 172 hit points and a head count that can grow make it far tougher than those numbers suggest. Wakeful means at least one head is always awake, so a sleeping hydra can't be ambushed the easy way. Hold Breath (1 hour) and a 30-foot swim speed let it wait underwater.

The Hydra in the 2024 Rules

The 2024 hydra (SRD 5.2.1) keeps the bite, AC, CR and the heads mechanic but changes several numbers that matter.

Two of these change how the fight plays:

• •Regrowth heals less in big rounds. In 2014, losing two heads in a round means four new heads and 40 hit points back. In 2024 the same round gives four new heads but only 20 hit points, because the 20 is a flat amount per regrowth, not per head.
• •The condition immunities are real immunities. A 2014 hydra with only one head left loses its advantage against stuns and fear. The 2024 hydra can never be Blinded, Charmed, Deafened, Frightened, Stunned or knocked Unconscious, no matter how many heads it has.

How the Multiple Heads Rule Works

The rule step by step, as both SRDs word it:

1. •The hydra starts with five heads. It makes one Bite per head with its Multiattack, and it gets one extra reaction per head beyond the first, usable only for opportunity attacks.
2. •25 damage in one turn kills one head. "Turn" means any creature's turn. If the fighter deals 25 or more on the fighter's turn, one head dies. If the wizard then deals 25 or more on the wizard's turn, a second head dies. One turn can only ever kill one head: 60 damage on the fighter's turn still removes a single head.
3. •The hydra keeps fighting with the heads it has. Heads lost before the hydra's turn are gone when it attacks. A hydra that lost two heads in the round bites three times, not five.
4. •At the end of the hydra's turn, it regrows. It grows two heads for each head that died since its last turn. In 2014 it regains 10 hit points per head grown this way. In 2024 it regains 20 hit points once.
5. •Fire stops all regrowth for that turn. If the hydra took any fire damage since its last turn, none of the dead heads grow back. The fire doesn't have to come from the attack that killed a head. A single Fire Bolt that hits, from anyone, at any point between the hydra's turns, is enough.
6. •No heads means a dead hydra. If every head is dead, the hydra dies, no matter how many hit points it has left. It also dies normally at 0 hit points.

Neither SRD sets a maximum number of heads. If the party keeps cutting without fire, the hydra keeps growing.

An example round against a 2014 hydra. The fighter deals 31 damage (one head dies). The rogue deals 18 (nothing). The wizard casts Fireball and the hydra fails its save, taking 28 fire damage (a second head dies). The hydra now has three heads and bites three times on its turn. At the end of its turn, it has taken fire damage, so nothing regrows. Next round it still has three heads. If the wizard's 28 damage had been non-fire (a Lightning Bolt, say), the same round would end with seven heads and 40 hit points healed.

How the Hydra Fights

A hydra is a melee engine. Everything it does happens within 10 feet.

Damage per round. Each bite is +8 for 10 average damage.

A +8 bite hits AC 16 on an 8 or higher, 65% of the time. The hydra can split its bites however it wants, so five bites can all go at the wizard who wandered into reach.

Opportunity attacks. With five heads, the hydra has four extra reactions for opportunity attacks, so five in total each round. Every character who walks out of its 10-foot reach can be bitten. In a fight where the party keeps repositioning, those free bites add up fast.

Use the water. A hydra holds its breath for an hour. In a lake, river or flooded ruin, it starts submerged, surfaces to bite characters on the bank or a boat, and drops back under where most characters can't follow. Characters without a swim speed spend 2 feet of movement for every 1 foot swum, while the hydra moves at full speed.

Let the table learn the rule. A smart DM lets the hydra lose a head or two to non-fire damage early, then counts the new heads out loud at the end of its turn. Players learn the rule from the table instead of from a lecture, and the next round they reach for fire.

Running a Hydra Encounter

A single hydra is a strong fight for four characters at level 6 or 7 and a dangerous one at level 5. Using the 2024 XP budget (the hydra is worth 3,900 XP):

The 2014 Dungeon Master's Guide guidelines, used by our encounter difficulty calculator, rate one hydra as Hard for four level 5 or level 6 characters and Medium at level 7.

Both budgets underrate the hydra against a party with no fire. A level 6 party of martial characters that can't deal fire damage will keep feeding it heads. Before you run it, check the party's spell lists and items. If nobody has fire, put a source in the room the party can find. The cheapest one is already in most packs: in both editions, a burning torch used as a melee weapon deals 1 fire damage on a hit, and 1 fire damage is enough to stop regrowth for the round. Oil flasks make the fire hit harder (a doused creature takes an extra 5 fire damage the next time it takes fire damage).

Bigger fights. Hydras usually work alone. If you want more, add creatures that keep the party in its reach rather than more hydras: lizardfolk that shove characters back toward the water, or a second threat on the shore that forces the party to split.

How Players Beat a Hydra

• •Bring fire, and spread it out. One instance of fire damage per round is enough to stop all regrowth, and it can land any time between the hydra's turns. The safest plan is to have the character who acts last before the hydra hold a fire attack in reserve, using it only if a head died and nobody has burned the hydra yet. Burning Hands works at close range, Fireball from a distance, the Fire Bolt cantrip costs nothing, and a torch swing (1 fire damage on a hit) counts too.
• •Count damage per turn. Every character who can deal 25 in one turn removes a head. A hydra with no heads is dead even with 100 hit points left, so with fire on the table, the head route is often faster than the hit point route. Five turns of 25 damage each kill it outright.
• •Without fire, focus on hit points. If there's no fire available, avoid crossing the 25 mark in a single turn when you can help it. That sounds backwards, but a 2014 hydra that loses one head grows two and heals 20, so a 26-damage turn is worth only about 6 damage and costs the party an extra bite every round.
• •Stay out of 10 feet. It has no ranged attack. A ranged party that can keep it at a distance takes no damage at all, and it has only 30 feet of land speed in 2014 (40 in 2024).
• •Target Charisma and Intelligence. Its saves are Strength +5, Dexterity +1, Constitution +5, Intelligence -4, Wisdom +0, Charisma -2. Banishment removes it on a failed Charisma save. Paralysis is not on its 2024 immunity list, so Hold Monster works on it in both editions. Hold Person does not, because it's a Monstrosity.
• •Skip the fear and charm spells. The 2024 hydra is immune to Charmed, Frightened, Stunned and three other conditions. The 2014 hydra rolls with advantage against them while it has two or more heads.

Hydra Encounter Ideas

The ferry crossing. A wide river has one ferry, and the ferryman stopped running it after something took the last crossing's mules. The hydra lives under the ferry landing. The ferry deck is a 20-by-30-foot raft on a rope, and the hydra can surface on any side. Lit lanterns and a barrel of lamp oil sit on the raft, which a quick-thinking player can turn into fire damage.

The overfed hydra. A mercenary band "killed" a hydra in the marsh last week by hacking at it with axes. They came back with five heads as proof and a story. The villagers now report a hydra with nine heads. The party gets the mercenaries' trophies, the mercenaries' bad advice, and a much bigger problem. The mercenary captain insists fire "only made it angry."

The temple pool. A drowned temple's central pool holds a hydra that the old priests kept as a guardian. The braziers around the pool still have oil in them but haven't been lit in a century. Lighting them takes an action each, under attack. A party that reads the faded murals before the fight learns what the braziers were for.

Fights like the overfed hydra stretch across sessions. Loreify can record your sessions and keep the notes, including how many heads the thing had when the party ran.

Frequently Asked Questions

How many heads does a hydra have in 5e?

A hydra starts with five heads in both the 2014 and 2024 rules. It can end up with more, because it grows two heads for each one that dies unless it took fire damage since its last turn. Neither SRD sets a maximum.

How do you kill a hydra's heads in 5e?

Deal 25 or more damage to the hydra in a single turn. That kills one head; more damage in the same turn doesn't kill a second one. If all its heads die, the hydra dies.

Does fire stop a hydra from regrowing heads?

Yes. If the hydra has taken any fire damage since its last turn, it grows no new heads at the end of its turn, even for heads killed by non-fire damage. One source of fire damage per round is enough.

Does acid stop a hydra from regrowing heads?

No. Only fire damage stops a hydra's regrowth. That's a difference from the troll, whose Regeneration is stopped by acid or fire.

What CR is a hydra?

A hydra is CR 8 (3,900 XP) in both editions. The 2014 hydra has 172 hit points and the 2024 hydra has 184, both with AC 15.

How much does a hydra heal when it grows heads?

In the 2014 rules, 10 hit points for each head it regrows, so 20 per head killed. In the 2024 rules, a flat 20 hit points whenever it grows new heads, however many there are.

Stat blocks: System Reference Document 5.1 (2014) and 5.2.1 (2024), Wizards of the Coast, CC-BY-4.0. Tactics, encounter math and ideas are Loreify's own.