Alchemical Hydra OSRS Boss Guide – Recommended Gear and Phases

Alchemical Hydra OSRS Guide
By | July 19th, 2021 | Categories: OSRS

There are many bosses to confront when playing Old School RuneScape, which can be very beneficial to you if you beat them. One such creature is the Alchemical Hydra OSRS boss, who you will find in the Karuulm Slayer Dungeon. If you have been struggling with this mighty beast, then this guide will come in handy.

Here you will find the following information regarding the boss:

  • Recommended Gear/Inventory
  • Where to Find the Boss
  • The Boss Fight
  • Poison Phase
  • Lightning Phase
  • Flame Phase
  • Enrage Phase

Recommended Gear/Inventory for Alchemical Hydra OSRS

There’s a few key items that you should take with you into battle. The Twisted Bow is ideal since it scales with how high the magic level is of your opponent. Equipping this with Dragon arrows will be super effective. Have the Slayer helmet, Necklace of Anguish and Max Cape as well. If you are using the blowpipe instead, try Ava’s assembler. If you’re using the blowpipe and are wondering what darts to use for Alchemical Hydra, we recommend sticking with adamant darts.

As for your inventory, have up to 20 prayer potions with you. Food is also going to be handy, as well as Antidote++. Ranging potions can also be very useful for an extra boost during the battle.

Where is Alchemical Hydra?

The Alchemical Hyrda serves as a level 95 Slayer boss. You will encounter this boss within the Karuulm Slayer Dungeon as part of a hydra task, which you need to be assigned to.

You can get to the boss by heading north beyond the Tasakaal. From there, go east where the hydras are. Once you have passed by them, you will eventually get to the lair entrance near Orrvor quo Maten. If you want to take a different route, then you will need to have level 88 Agility to do so. This means you can use the pipe found behind Kaal-Ket-Jor. This isn’t necessarily quicker however, so it doesn’t make much difference which path you take.

Fighting the Alchemical Hydra OSRS Boss – Phases

This is an instanced fight, so if you die you will get your items back via Orrvor quo Maten. However, you will need to fork out 100,000 gold to get them back. Not only that, but if you die in another location whilst he has your items they will be gone.

With the Hydra in the room, you won’t be able to get out through the doors. If you wish, you can teleport out, and you’d need to wait for 20 seconds for the Hydra to respawn. As far as attacks go, the Hydra is capable of both magic and ranged offence. This rotates after three attacks no matter if they’re successful. The ranged attacks you’ll notice are fanged projectiles, whilst magic are small and green.

The heads to the sides are what the Hydra will be mainly using to attack you with. The left uses magic, and the right uses ranged, with the middle head not attacking you. In the first couple of phases, you will find that the attacks hit twice, and the attacks for each respective sides are reduced once the lower heads fall off. What you need to be aware of is that the Hydra is high level in both ranged and magic. Thankfully, its defence is low, and if you have dragon hunter weapons you can do bonus damage.

Poison Phase

During the poison phase, you will see  agreen carapace. This means you should lure towards the red pool that you see. Once killed, go and stand by the red chemical vat to lure the Hydra into it. Following the first three attacks, the Hydra starts lobbing poison orbs at you. They have a splatter effect of 3×3 and land on your as well as four random places around you. To avoid this, head west where the red chemical vat is, then go south. Move two tiles north of the Hydra near the pool, then go west two tiles again to avoid the splatter.

Eventually, you’ll get the Hydra down to 75% health, which sees the head in the bottom-right falling off. The carapace turns blue, so head north to where the green vent is.

Lightning Phase

In this phase we want to lure the Hydra towards the green pool. As the name suggest, you will be getting electric hurled at you. This takes place in the middle of the room, after which four currents of lightning spawn in the corners of the room. These will move towards you, so loop around to avoid them. Sticking to the wall to the north is very effective here, before moving to west as you attack the Hydra. You can also trap the lightning if you were to head to the north-western area and go to the corner.

As the Hydra’s health depletes to 50%, you will see the carapace change to red. Go west of the blue vent and get ready for the next phase.

Flame Phase

Next, we are luring the Hydra over to the blue chemical pool. During the flame phase, you will notice the Hydra heading towards the middle of the room and look in your direction. You will be forced out if you’re positioned under the Hydra, and you need to look out for a fire-breathing attack that covers 5×5 in area. This will track the player and get faster if you run, so try walking straight in a line to evade it.

At 25% health, the carapace changes to grey, which takes us onto the final phase.

Enraged Phase

You won’t need to lure to any chemical pools when in this phase. The enrage of the Hydra stacks and you’ll get a warning to say that is has become enraged. This is a part of the fight where having prayer and health will be useful, since it only takes two hits from the Hydra to kill you.

This phase will see the opposite approach to combat from the last phase. The styles now change after every attack. The poison attack also makes a return, and can be in the same form as it was in the first phase. The poison offence comes back in after three auto-attacks, after which it will be for nine auto-attacks subsequently. Keep using your prayer and the Hydra will soon be down for the count.


There you have it, you finally defeated the Alchemical Hydra OSRS boss! Preparation is the key to success of this fight, so make sure to have the right gear and health items with you. Prayer is going to be vital, and knowing where attacks are going to hit will be a real difference maker.

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