The short version
30-second read- Kraken at 87 is the gentlest high-level boss. Melee cannot damage it and its typeless hits ignore prayer, so bring a magic setup and enough food.
- Alchemical Hydra punishes ignoring the vents. It takes 75% less damage in each of its first three phases until you lure it over the right chemical vent.
- Cerberus is a counting fight. Triple attacks come first and every tenth attack, souls every seventh below 400 HP and lava every fifth below 200 HP.
- Grotesque Guardians need a brittle key first. Priest in Peril is required too, and gargoyles on task drop the key for the first visit.
All 8 Slayer Bosses, Easiest to Hardest
Old School RuneScape has eight Slayer bosses: Shellbane Gryphon (51 Slayer), Grotesque Guardians (75), Abyssal Sire (85), Kraken (87), Cerberus (91), Araxxor (92), Thermonuclear smoke devil (93) and Alchemical Hydra (95). Every one of them needs the Slayer level and the matching task, so you fight them when the task comes up. In our ranking the easiest are Kraken and Thermonuclear smoke devil, and the hardest band is Grotesque Guardians, Abyssal Sire, Araxxor and Alchemical Hydra.
We rank by mechanical difficulty rather than profit. Profit rankings go stale every time the Grand Exchange moves, while a boss's Slayer requirement and its mechanics only change when Jagex changes the content.
| Boss | Difficulty | Slayer level and task | Notable reward |
|---|---|---|---|
| Kraken | 2 / 5 | 87, cave kraken task | Trident of the seas, kraken tentacle |
| Thermonuclear smoke devil | 2 / 5 | 93, smoke devil task | Occult necklace, smoke battlestaff |
| Cerberus | 3 / 5 | 91, hellhound task | Primordial, pegasian and eternal crystals, smouldering stone |
| Shellbane Gryphon | 3 / 5 | 51, gryphon task, plus Troubled Tortugans | Belle's folly (tarnished) |
| Grotesque Guardians | 4 / 5 | 75, gargoyle task, plus a brittle key the first time | Black tourmaline core, granite gloves, granite ring |
| Abyssal Sire | 4 / 5 | 85, abyssal demon task | Unsired: bludgeon pieces, abyssal dagger, abyssal whip |
| Araxxor | 4 / 5 | 92, spider or araxyte task | Noxious halberd pieces, araxyte fang |
| Alchemical Hydra | 4 / 5 | 95, hydra task | Hydra's claw, hydra leather, brimstone ring pieces |
Which Slayer Boss Is the Hardest?
There is no official difficulty list, so this is our call. If you want a single name, it is between Alchemical Hydra and Araxxor. Hydra has the highest Slayer requirement at 95, takes 75% less damage in each of its first three phases until you lure it over the right chemical vent, and its grey enrage phase attacks every four ticks for up to 55. Araxxor is the highest-levelled Slayer boss at combat level 890 with 1,020 hitpoints, and you have three kinds of araxyte hatching around him while you fight.
The other two in the top band are hard in narrower ways. The Abyssal Sire puts most of its danger into one moment: when it drops under 140 hitpoints it teleports you next to it and explodes for up to 96. Grotesque Guardians is two bosses, Dusk and Dawn, with 450 hitpoints each on the Slayer Tower roof, and the fight changes every time they swap.
At the easy end, Kraken is killed with magic, since melee cannot damage it and ranged does a seventh of normal damage. Its 28 max hit is typeless, so prayer does not reduce it, and the fight is mostly about bringing enough food. Thermonuclear smoke devil has 240 hitpoints and hits for at most 8. Neither tests much beyond your supplies.
Slayer Bosses in Unlock Order
If you are training Slayer, this is the order the bosses open up. All of them also need the task, and several can be assigned as a boss task once you have the right unlock.
| Slayer level | Boss | Other requirements | Difficulty |
|---|---|---|---|
| 51 | Shellbane Gryphon | Troubled Tortugans | 3 / 5 |
| 75 | Grotesque Guardians | Priest in Peril, and a brittle key (dropped by gargoyles on task) for the first visit | 4 / 5 |
| 85 | Abyssal Sire | Partial Fairytale II for fairy ring DIP, or the Wilderness route through the Abyss | 4 / 5 |
| 87 | Kraken | 50 Magic to be assigned cave kraken | 2 / 5 |
| 91 | Cerberus | None | 3 / 5 |
| 92 | Araxxor | Priest in Peril | 4 / 5 |
| 93 | Thermonuclear smoke devil | None | 2 / 5 |
| 95 | Alchemical Hydra | None | 4 / 5 |
Shellbane Gryphon is the outlier. At 51 Slayer it is the first Slayer boss most accounts can fight. Vannaka, Chaeldar and Mortimer assign gryphons with no unlock, Nieve and Duradel only after you buy Wings Spread for 80 Slayer points, and Konar can give the gryphon itself as a boss task.
What Each Slayer Boss Tests
Gear that carries you through one of these can leave you stuck on another, because each fight asks for something different.
| Boss | Difficulty | What it tests |
|---|---|---|
| Kraken | 2 / 5 | A magic setup and enough food. Melee cannot damage it, and its typeless hits ignore prayer. |
| Thermonuclear smoke devil | 2 / 5 | Getting smoke devil tasks. The fight itself is 240 hitpoints and an 8 max hit. |
| Cerberus | 3 / 5 | Counting: triple attack first and every tenth attack, souls every seventh under 400 HP, lava every fifth under 200 HP. |
| Shellbane Gryphon | 3 / 5 | Gear weight: 40 kg or more equipped stops its knockback, and the tortugan shield lets Protect from Melee block its melee fully. |
| Grotesque Guardians | 4 / 5 | Two bosses on one roof, Dusk and Dawn, and the phase swaps between them. |
| Abyssal Sire | 4 / 5 | Phase order: stun it, break four respiratory systems, then escape a 96 explosion under 140 HP. |
| Araxxor | 4 / 5 | Add control: acidic, mirrorback and ruptura araxytes hatch from eggs, and the enrage under 25% speeds him to 4-tick attacks. |
| Alchemical Hydra | 4 / 5 | Room knowledge: the vent for each carapace colour, then a grey enrage phase with prayer switches on every attack. |
Bosses People Mistake for Slayer Bosses
Three more fights turn up on Slayer boss lists, but none of them is one in the strict sense:
- Skotizo has no Slayer level. You use a dark totem on the altar in the centre of the Catacombs of Kourend, one totem per attempt, and kills count towards black demon and greater demon tasks.
- Basilisk Knights are a Slayer monster rather than a boss. They need 60 Slayer and The Fremennik Exiles, live in Jormungand's Prison, and drop the basilisk jaw for the Neitiznot faceguard at 1/1,000 on task or 1/5,000 off it.
- Maggot King is a solo boss in Vampyrium unlocked by The Blood Moon Rises, with no Slayer level. Konar, Nieve and Duradel can assign it as a boss task.
FAQ
How many Slayer bosses are there in OSRS?
Eight: Shellbane Gryphon, Grotesque Guardians, Abyssal Sire, Kraken, Cerberus, Araxxor, Thermonuclear smoke devil and Alchemical Hydra. Skotizo and Maggot King are sometimes listed too, but neither needs a Slayer level.
What is the hardest Slayer boss?
Alchemical Hydra or Araxxor, in our view. Hydra has the top Slayer requirement (95) and a vent mechanic that cuts your damage by 75% if you ignore it; Araxxor has the highest combat level (890) and adds to manage on top of the boss.
Can I fight Slayer bosses off task?
No. All eight need the matching task. The exceptions are one-offs, such as a single Thermonuclear smoke devil kill for the Western Provinces Diary, which still needs 93 Slayer without a boost.
Which Slayer boss is worth the most?
We do not publish a profit ranking, because it would be wrong within weeks of the next Grand Exchange move. The reward column tells you what each one drops; check current prices on the OSRS Wiki and decide from there.
Still stuck on a mechanic? Ask the team on our Discord, it is free.
Bottom Line
Start with whatever your Slayer level opens first: Shellbane Gryphon at 51, then Grotesque Guardians at 75. Of the high-level bosses, Kraken at 87 is the gentlest, and Alchemical Hydra at 95 is the last one to unlock and the hardest to learn.
If the Slayer level is the wall rather than the fight, our Slayer training is done by hand. Each row in the tables above links to its own guide for gear, mechanics and drops.
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