OSRS Boss Gear & Inventories

Alchemical Hydra

Combat level 426 · 1100 hitpoints

A four-phase colour-changing hydra and the single best gear-progression slayer boss: Hydra leather (Ferocious gloves), Hydra tail, Brimstone ring and the Dragon hunter lance all drop here.

Requirements

• 95 Slayer
• Hydra task
• Karuulm Slayer Dungeon (boots of stone)
• 70+ Prayer strongly recommended

Pointers

• Four phases, each a colour. Green: alternates ranged/magic every 3 attacks. Blue: same, plus poison pools. Red: same, plus a flame wall. Jad phase: alternates ranged/magic EVERY attack.
• At each phase transition it walks to a chemical vent. Attack it there to skip the enrage, or it gains a damage buff.
• Boots of stone (or brimstone/granite boots) are required just to walk the Karuulm dungeon floor.
• Prayer switching is the entire fight. If you cannot flick reliably, do not bring expensive gear.
• It is weak to STAB and to ranged. The Dragon hunter lance it drops is also the best melee weapon against it once you have one.
• Bring an Anti-venom+. The blue phase poisons heavily.

What the sim brings here

Every worn slot and every inventory row below is the combat simulation's own output, at the style it ranks fastest for each account tier. Each line carries the channel that chose it: sim means the model solved it, and inherited means the value came through from the hand-authored loadout the solver starts from. Riding through a generator does not make a value derived, so those are marked rather than presented as the model's answer. A line marked unattributed carries a channel the model's own vocabulary no longer declares, so no word is put on it at all rather than one being read off the channel's spelling. Where the model has not answered a row, its own refusal is printed instead; where it has answered a row it doubts, the answer is printed with the doubt attached rather than withheld.

What each of those badges means

• derived:ascent (sim): an accepted coordinate-ascent move: betterThan() preferred this candidate over the incumbent under the row objective and band. The weapon+ammo+shield pairing and the crystal set arrive here too, because both are offered to the same acceptance test.
• derived:composed (sim): balanceInventory() sized this row from the derived supply menu. The menu enumerates CONSUMABLES and narrows by style, tier and price; it is not the authored bag.
• derived:empty (sim): the finished loadout leaves this slot EMPTY, and that is an ANSWER rather than a gap: a two-handed weapon forfeits the shield and a weapon that stores its own ammunition frees the ammo slot. Recorded so a null slot is never read as unprovenanced.
• derived:pouch (sim): derivePouchInto(): the rune pouch and its loose overflow, from the spell the build actually casts and the pouch slot criterion. Not from a pouch a human typed.
• derived:spec (sim): a carried special-attack weapon PROPOSED by `specPlan` (specchoice.js), which prices every SPEC_ATTACKS weapon that deals damage or drains defence on top of the bag solved without one, and KEPT by `judgeSpecArms` only where the composed bag with it beats the bag without it under `compareScores`. The row's `kpt.specWeapon` carries both arms.
• derived:travel (sim): travelPlan(): the way IN, ranked out of the derived transport graph against this account's own unlocks, rather than copied from whatever a human typed. The way OUT is a separate channel (`ruled:escape`) because it is a typed choice, not a ranking.
• derived:voidSeed (sim): the Void set offered assembled, because an all-or-nothing set effect pays nothing until four slots are right and every single step toward it is a strict loss. The pieces come from VOID_SET in combat.js, the same names its own predicate tests.
• ruled:escape (ruled): escapeLeg(): the way OUT, taken from the typed per-tier table ESCAPE_PLAN and judged against the account, with nothing substituted and no fallback ladder. The ACCOUNT CHECK is a derivation; the CHOICE of item is not, so this is not a `derived:` channel. ESCAPE_PLAN carries no attributedTo field (PROVENANCE_BACKLOG: silent-and-unattributed), so this channel does not claim one either.

Alchemical Hydra strategies on the OSRS Wiki