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Alchemical Hydra

The Alchemical Hydra is a boss found in lower level of the Karuulm Slayer Dungeon in Mount Karuulm, requiring level 95 Slayer to kill. The Alchemical Hydra was the creation of an unnamed dragonkin. While the Dragonkin saw promise in his creation, he nevertheless saw it as a failure because he could not replicate its traits, and abandoned it along with his other creations; the Wyrms, Drakes, and Hydras.

Unlike normal hydras, the Alchemical Hydra can only be killed while on a hydra slayer task, which are only assigned by the hard and elite slayer masters, also requiring a streak of three slayer tasks. In addition, as it is only found within the volcano, players who are not donor or premium players must wear boots of stone or boots of brimstone to protect themselves from the extreme heat of the dungeon floor.

Along with all the unique drops obtainable from hydras, it can also drop hydra leather, which is used on the machinery south-west of the pool in the Lithkren Vault to create ferocious gloves, as well as the hydra claw, which is combined with a Zamorakian hasta to create the dragon hunter lance.

Fight overview

The fight is instanced; if players die while fighting the Hydra their items will remain in their inventory. The Alchemical Hydra uses both ranged and magic attacks against players. It changes its attack style after every three attacks regardless if they hit or not. The magic attacks consist of two small green projectiles, while the ranged attacks are fanged projectiles.

During the first three phases, the Hydra has heavy damage reduction, which can only be removed by being sprayed with the correct chemical. The pools cover a 5×5 AoE, with the vent being the centre of that AoE. When the Hydra is in range and sprayed with the correct chemical, it roars and its damage reduction effect is removed for the duration of the phase. If sprayed with the wrong chemical, it adds enrage stacks which increase the damage of its auto-attacks.

Poison Stage

In this phase, the hydra starts with a green carapace, and should be lured to the red chemical pool. After the first kill, the player should stand right next to the red chemical vat (to the west) so that the Hydra is automatically lured to the red chemical pool as soon as it spawns.

After the first three attacks, The Alchemical Hydra will launch 4 or 5 poison blobs around the player's location; 1 on the player, and 4 randomly around it. The blobs have a 3×3 splatter effect dealing up to 7 damage, and standing on the poison pools will deal up to 12 poison damage per tick. Both will cause a poison effect that deals 4 damage; if players get poisoned, immediately clear its effects. The best way to avoid this attack is by standing west of the red chemical vat, all the way south, then move north two tiles when the Hydra is positioned over the chemical pool. When it spits poison, move west two tiles - this avoids the one targeting the player, and the other four will splatter east.

Once the Hydra reaches 75% of its health, the bottom-right head falls off, and it changes its carapace to blue. Next, the player should run north to the green vent.

Lightning Stage

Throughout the phase, the Hydra will launch an electric ball in the center of the room, which spawns four lightning currents in the four corners of the chamber, although the order in which they appear in is random. The four pieces of lightning converge on the player's location. Getting hit by them will bind the player and deal up to 20 damage. Starting near the middle of the room and looping around one of the last lightning spawns, to escape the box they form, is the easiest way to avoid their damage. Players may also hug the northern wall and quickly move their way west while damaging the Hydra, which works especially well with any ranged weapon with a distance of 10. It is possible to trap the lightning by standing in the north-west corner, moving one tile diagonally south-east when the lightning is two tiles away from you, and instantly moving one tile north. This does not despawn the lightning, so if the player were to move off of the tile, the lightning will start following them again.

Once the Hydra reaches 50% of its health, the bottom-left head falls off and it changes its carapace to red. Next, the player should run west to the blue vent if not already there from the lightning.

Note: If the Hydra transitions to the next phase while there is lightning on the field, they will dissipate immediately.

Flame Stage

Throughout the phase, the Hydra will occasionally walk to the centre of the chamber and face the direction the player is at. Once it reaches the centre, the player is stunned, but they can still attack the Hydra. If the player is underneath the Hydra, then it forces them out into a random direction. Upon reaching the centre, it breathes 5×5 layer of fire to the player's sides based on their location before staring down the middle and launching a tracking fire. This tracking fire follows the player's movement, and travels significantly faster the further the player is (or if they start running). Turning off run and walking in a line as the fire trails is the best course of action. Getting hit by any of the fires will result in the player taking up to 20 damage, followed by a subsequent bleed of 5 damage for five hits. Moving onto another fire resets the bleed. Fires may be tile skipped, though it's only recommended to do so after the tracking fire stops. The Hydra does not attack until four seconds after the tracking fire is sent out.

Once the Hydra reaches 25% of its health, the middle head falls off and it changes its carapace to gray.

Note: If the Hydra transitions to the next phase while performing this attack, it ends abruptly.

Enraged State

There is no counter to the grey carapace; do not lure it to any of the chemical pools for this phase. As such, it does not need to be lured as its damage reduction ability does not reset. The Hydra's enrage stack will increase to max, with the message “The Alchemical Hydra becomes enraged!”. It is capable of killing players in two hits, so health and prayer must be kept high.

The Hydra starts off this phase by attacking with the combat style opposite of what it used in the previous phase; if the previous phase ended with a magic attack, then it starts with ranged and vice versa, even if it was the final hit before switching attack styles. In addition, it switches combat styles after every attack, much like Zulrah's unusual green form in the penultimate step of each rotation.

It also uses the poison attack from phase 1, though it generally sends one poison blob on the tile it is on; however, it can still use the phase 1 variant of the attack, if the fires from the 3rd phase have subsided, and the poison effect increases from 4 damage to 6. During this final phase, the Hydra spits poison after the first three auto-attacks, then nine auto-attacks for subsequent poison attacks. Continually pray flick until the Hydra is killed. It is recommended to keep prayer points up to prevent the possibility of the Hydra landing a hit on the player. If the Hydra is killed just as it sends an attack, it will deal no damage.

Fight Technique

Following the order of the colors, as noted earlier, move the Hydra to the proper chemical spout to weaken the beast. In the first phase, simply move out of the way of the poison. In the second phase, simply move away from the lightning. In the third phase, simply move out of the way of the fire. The final phase may require more poison dodging.