820 (410 Armor, 410 Health) (Support)
The Bone Hydra is what remains of the Lernaean Hydra, slain by the demi-god hero Heracles as part of his Twelve Labors. It now dwells in the fiery Phlegethon river that flows through Asphodel, and guards the passage to Elysium.
The Bone Hydra is the boss encounter for Asphodel, as well as the second boss encountered in every run of Hades. They are always encountered at Chamber 24, the final Chamber of Asphodel.
The Bone Hydra is fought in its own unique chamber. This chamber is shaped like a semi-hexagon island surrounded by magma, with pots containing healing in the top 2 corners of the island. It also features 4 indestructable pillars which are placed in the more center area of the island. The Hydra rests at the top edge of the island, only extending down to the center of the island when Lunging.
The Bone Hydra's attacks start off relatively simple and grow more complex as the fight goes on. It begins the fight with three abilities: Lunge, Volley, and Ground Slam.
- Lunge: The Hydra's head charges in the direction of Zagreus after a brief delay dealing 5 damage.
- At 66% max HP, Lunge's damage increases to 16. The Support Heads continue to deal 5 damage.
- Volley: The Hydra's head retreats back to the top of the island and launches a stream of five slow moving dart projectiles which home in on Zagreus' current position.
- At 66% max HP, Volley becomes Barrage. The Hydra quickly retreats to the top edge to launch a large amount of fast moving dart projectiles in Zagreus' direction and general area, which will circle around the arena and home in on him. While at least one Support Head is alive, this attack reverts back to Volley.
- Ground Slam: The Hydra's head slams itself into the ground beneath it, dealing 16 damage in a shockwave around it.
- At 33% max HP, Ground Slam becomes Triple Ground Slam, and causes the Hydra to slam its head into the ground beneath it three times in quick succession. The head is able to move towards Zagreus a short distance between each bounce. The Melee Support heads do not gain access to Triple Ground Slam, and will only attack with their normal Ground Slam.
It also has 4 Variant options it can become after the player has killed it three times, based on what the Support Heads can do.
- Slammer (White-Blue Variant) - Ground Slam: Causes up to 10 pieces of rubble to fall on the stage, dealing 9 damage each. Cannot Volley.
- At 66% max HP, Ground Slam becomes Triple Ground Slam, and causes the Hydra to slam its head into the ground beneath it three times in quick succession. The head is able to move towards Zagreus a short distance between each bounce. Each bounce causes rubble to fall.
- At 33% max HP, Ground Slam becomes Super Ground Slam, and causes the Hydra to slam its head into the ground beneath it one to six times in quick succession. The head is able to move towards Zagreus a short distance between each bounce. This attack can cause 10~40 pieces rubble to fall, regardless of how many times it bounces.
- Ranged (Orange Variant) - Magma Spittle: Bone Hydra's Volley ability is replaced by the Magma Spittle of the Orange Support Heads. Spews 3-5 fireballs which cover sections of the arena near the head with temporary magma.
- After being reduced to 66% max HP, gains additional ability to spew 8-11 fireballs in a circle around itself (instead of Barrage). Unlike Barrage, this ability is not lost while Support Heads are active.
- Summon (Green Variant) - Super Hydra Teeth: Spits out an orb with 50 HP and 35 Armor that spawns an Elite Bloodless Bone-Raker unless destroyed within 5 seconds. Can also summon a Skull-Crusher to fall on Zagreus. It dies immediately after landing.
- At 66% max HP, it can spit out 2 orbs at once when Support Heads are inactive. Can also summon two Skull-Crushers in succession.
- At 33% max HP, it can spit out 3 orbs at once when Support Heads are inactive. Can also summon three Skull-Crushers in succession.
- Control (Purple Variant) - Waves: Volley is replaced with a row of wave attacks.
At 66% and 33% max HP, the Hydra retreats, becoming invulnerable and spawning increasing numbers of additional "Support Heads" at fixed points around the edge of the arena. These additional heads have their own abilities and must be defeated before the main head will become vulnerable to attack again.
- At 66% max HP, it summons 3 Support Heads in the edges of the arena.
- At 33% max HP, it summons 6 Support Heads in the edges of the arena.
NOTE: DoT effects applied before the Hydra became invulnerable will not cause damage once it becomes invulnerable between rounds.
Each Support Head has access to the Lunge attack, and one other attack:
- Standard (Yellow) - Volley: Have access to the Volley attack the base Head has, with less damage.
- Melee (White-Blue) - Ground Slam: Have access to the Ground Slam attack the base Head has, with a smaller radius.
- Control (Orange) - Magma Spittle: Spews out 3-4 fireballs which cover sections of the arena near the head with temporary magma.
- Summon (Green) - Hydra Teeth: Spits out three orbs with 50 HP which spawn a Bloodless unless destroyed within 5 seconds.
- Ranged (Purple) - Waves: Releases wave attacks in Zagreus's direction which deal 11 damage and cause Knockback on contact.
When using the second rank of the Extreme Measures condition of the Pact of Punishment, the Bone Hydra's arena will change. Rather than one large island with the Hydra tethered to the topmost edge, it will instead be fought in the center of a smaller island split up by streams of magma. There are no permanent pillars in this arena, but there are a number of breakable pillars scattered around.
When summoning Support Heads, instead of being trapped to the left, right, and bottom edges of the island, they will spawn on all four sides of the island. The main head will remain in the middle.
Upon reaching 66% health, the Bone Hydra will shatter the neck keeping it tethered to the center of the arena before summoning the support heads. The now-disembodied head will begin to chase Zagreus around the arena, frequently lunging at Zagreus and triple ground slamming. It will continue to act like this even after all 6 of its Support Heads are vanquished. It is still invulnerable while its Support Heads are alive.
After being reduced to 33% max HP with Extreme Measures, it will lose the ability to use Volley or Barrage for the rest of the fight.
When defeated, the Bone Hydra drops a Diamond if Bounty conditions are met. This means that either it must be Zagreus' first victory against it with a weapon, or the Target Heat must be met for that weapon. Otherwise, it will drop 100 . The Darkness reward is affected by Boons and bonuses (Dark Thirst, Poseidon's Ocean's Bounty, Chaos's Eclipse, etc.)
After picking up the reward, the door on the opposite side of the chamber will open, allowing Zagreus access to the Stairway Chamber between Asphodel and Elysium. In the chamber is a Healing Fountain, a Well of Charon, Pool of Purging, and the Keepsake Display Case (if it has been purchased at the House Contractor).
- The orbs spawned by the green heads are referred to in the game files as "Hydra Teeth". This may be a reference to the "dragon's teeth" mentioned in the Argonautica, which sprung up into skeletal warriors when sown in the ground.
- The Hydra's full name was misspelled prior to the Good Times update, missing the first A out of Lernaean.
- The Bone Hydra was the final boss of the game prior to Patch 018, the first patch of the Beefy Update.
- As of the Long Winter update, Zagreus can decide to nickname the Bone Hydra "Lernie". The Hydra's health bar is then labelled Lernie the Bone Hydra in all subsequent fights.
- After the Hydra is nicknamed "Lernie", the post-victory sign is changed from "Hydra Vanquished" to "Lernie Vanquished".