The Great Olm (referred to as the Guardian in the Deep by Xeric's followers) is the final boss in the Chambers of Xeric raid. A large, blind, white salamander, it is one of Xeric's greatest possessions.
Chambers of Xeric can only become a Slayer task through a Choose Wisely scroll (2–5 raids); Krystilia never assigns it at random. Only finished raids count, in normal or Challenge mode: when the raid is completed, every player in it who has the task gets one raid off it and 30,000 Slayer experience before the Slayer XP boosts. Slayer bracelets do not work on raid tasks. The task teleport takes you to the Chambers of Xeric.
Mechanics
Fighting the Great Olm's claw in its crystal chamber at the end of the Chambers of Xeric (::cox), with the Olm's head rising out of the wall
Attacks
Standard attacks: Olm has two standard attacks: Magic and Ranged. The magic attacks are large green orbs, while the ranged attacks are smaller chunks of crystal. Both deal the same amount of damage. The correct protection prayer reduces the damage by 70%.
Spheres: Olm randomly picks a sphere (red, green or purple) and sends it at the player. If not blocked, the player will be damaged approximately 50% of their current Hitpoints. If a protection prayer was used when the sphere was launched, it is disabled and the player's Prayer is reduced by 50%. To block the attack, pray accordingly before and as the sphere hits you:
Red (sphere of aggression): Protect from Melee
Green (sphere of accuracy and dexterity): Protect from Missiles
Purple (sphere of magical power): Protect from Magic
During phases 1-3, Olm also has access to these specific attacks:
Crystal Burst: Olm throws a crystal seedling under every player in the chamber. A few seconds later, the crystals burst and shove the player to a nearby tile if they are on top of them for heavy damage. The left hand will briefly show a crystal icon when using this attack.
Lightning: Shoots out lightning running north and/or south of the chamber. Getting hit by a bolt of lightning electrocutes the player, disabling their overhead prayers, dealing moderate damage, and binding them. The left hand will briefly show a lightning bolt when using this attack.
Swap: Olm will perform a teleport attack that deals damage the further the player is from the target. The left hand briefly shows a swirl when using this attack. If alone, Olm will pick a random tile anywhere in the chamber; if there are more players in the room, Olm will evenly distribute the amount of teleports. If there is an odd-numbered amount of people inside, then those people will not be subjected to the attack.
Olm also has phase-unique attacks which can replace one of the auto-attacks in his rotation:
Acid:
Acid Spray: Olm spits out several pools of acid around the chamber. Standing on top of an acid pool deals 3-6 damage per tick and inflicts poison starting at 2 damage.
Acid Drip: Olm covers a player in acid, causing them to generate acid pools under them. Standing still will deal damage and moving will generate more pools, though it is not much of a deal in small groups. The pools function the same way as the pools in the spray attack.
A group of players fighting the Great Olm.
Flame:
Deep Burn: Olm shoots out a green fireball at a player, causing them to yell "Burn with me!". The targeted player takes 5 damage every few ticks, dropping stats by 2 each time this occurs for six hits. If it spreads to other players, the timer resets and newly infected players will initially yell "I will burn with you."
Fire Wall: Olm shoots out two walls of fire at a player to trap them. If the player is on a tile that would be occupied by the fire wall, they will leap out and take 8-10 damage in the process. After the walls are placed, players in the tiles between the two walls will take 50-65 damage in 5 seconds if they do not escape. Any water, such as water spells, ice spells, Humidify or a filled watering can will suffice in dousing a segment of flame.
Crystal:
Falling Crystals: Olm lets out a cry, targeting one player with a red aura. 11 spiked crystals fall from above, dealing up to 15-20 damage to anyone in the targeted tile.
Crystal Bombs: Olm shoots out a crystal bomb (up to three at most; two for smaller groups). The bomb explodes after being deployed for several seconds, covering a radius of four tiles. The minimum amount of damage dealt is 15, increasing by an additional 15 damage for every tile closer to it.
There are also attacks applied during other segments of the fight:
Autoheal: During the first three phases, any attacks aimed at the head are completely healed after several ticks have passed. In the third phase, the left arm also gets a variant of this ability where any attacks that deal damage will cause it to heal instead. When this is performed the left hand shows an infinity symbol.
Falling Crystals: During phase transitions and the last phase, Olm causes chunks of crystal to fall from above. These crystals have a 3x3 AoE; getting directly hit (underneath the shadow) by them will deal 16-25 damage, while getting indirectly hit (one tile from centre) deals 10-16 damage. One crystal will always be aimed at a random player in the chamber. A shadow will indicate where the crystal will land.
Life Siphon: In the last phase, Olm will shoot out two blue projectiles which generate a shield when it hits the ground. Several ticks later, Olm will damage anyone not on the targeted tiles for moderate damage, healing himself for five times the total amount of damage it deals to the team.
Fight overview
"Safespots" against Olm.The mystical barrier which precedes the boss fight.
Olm has at least four phases, with an additional phase for every 8 players in the raid. Unlike the other bosses in the room, once the player enters his chamber, it is a fight to the death. In each phase except the penultimate and final ones, Olm will focus on a specific set of abilities referred to as powers.
On Roat Pkz, Olm's hitpoints go up by 50% and its other stats by 20% for every extra player in the raid, despite him having a pre-determined combat level. This applies to the head and both claws. In Challenge mode the head is stronger (1,600 hitpoints). If stat draining attacks — such as dragon warhammer special attack — are used, they only affect the part of him that was hit. His stats also reset when a new phase starts.
Olm attacks with ranged and magic, the former consisting of a chunk of crystal and latter green-coloured dragonfire. There is a 1/5 chance the Great Olm will switch between these attack styles each time its head performs an attack. Olm has three attack zones to choose from; left, middle and right. He prioritises the zone with the most amount of players. If no players are in that zone, he will swerve his head accordingly and skip an attack in its attack rotation. If a player is in his attack zone but Olm swerves his head regardless, no attacks are skipped.
Olm's attack rotation consists of the following below. Phase-specific attacks are incorporated into the attack pattern as an auto-attack and alternate between the available pool:
2 auto-attacks
Crystal Burst
2 auto-attacks
Lightning
2 auto-attacks
Teleport
Loops from above
There is a 1/3 the Great Olm will carry out a phase-specific attack in lieu of an auto-attack (provided they are not on cooldown), increasing to a 1/2 chance during the final phase of the encounter. When this roll succeeds, the Great Olm will consequently try to avoid picking any of the available phase-specific attacks it has already used before.
In order to progress to the next phase, both of Olm's hands must be disabled. The Olm's left hand will clench if it takes a particularly heavy hit, equal to at least 1/20 of its base health. Olm's head can be attacked at any phase, although he will automatically recover any damage taken shortly afterwards in all but the final phase. When both hands are disabled, Olm will retreat underground and shake the area with AoE falling crystals before reappearing on the other side with a new power. During the penultimate phase, the left hand gains a damage to health ability indicated with an infinity sign on it. In this phase, both of Olm's hands must be disabled within a specific time frame or it will recover back at full health. All powers are available to Olm during this phase, and it is indicated with Olm's head glowing.
Once both hands are disabled, Olm remains on the spot and attempts a final stand. AoE crystals will continually fall from above until Olm is killed. As with the previous phase, he has access to all of its powers.
Setups by price
These setups come from what players wear when they kill the Great Olm, the last boss of the Chambers of Xeric. Each tab shows the gear most players use at that price, what it costs, and how long a whole raid usually takes with it. Prices are in PK points (PKP) at today's in-game prices, and spawnable items are free to spawn. The raid potions in the inventories are handed out free inside the raid. Almost everyone fights the Great Olm with ranged.
The Dragon hunter crossbow is 30% more accurate against the Great Olm, which counts as a dragon.
Most low-tier raiders carry a melee switch (Abyssal tentacle and Bandos armour, with a Bandos godsword for its special attack) and a magic switch (Trident of the swamp and Ahrim's robes).
Max-tier players bring full melee and magic switches for the rooms that need them: a Scythe of vitur set and a Tumeken's shadow set.
The switches are what make this tab expensive: the gear you wear at the Great Olm costs about 23M.
Equipment
Note: The equipment layouts below is for melee only, with magic and ranged switches in the player's inventory due to all three combat styles being required.
↑Xeric's aid (+)(4), Revitalisation (+)(4) and Prayer enhance (+)(4) can be spawned, which saves time.
↑The Bandos Godsword special attack drains more defence than the Dragon Warhammer's special attack after two hammers or more have successfully landed.
↑Additional items brought to speed up the raid include: Zaryte crossbow + Ruby bolts (e), Voidwaker, Dragon claws.
Chambers of Xeric Drop Rates
There are two drop tables: UNIQUE and DEFAULT.
You earn 7.5 points for every damage you deal to the Great Olm and its claws.
With 500 points or less you only get a cabbage. With 501 - 3,000 points you only get 1 - 500 Pk points.
For every 3,000 Points you receive, you have a +1% (changes based on Donator Rank) chance of landing on the UNIQUE drop table. Meaning if you solo a normal raid without dying you would receive 32,000-ish points or a 10% chance of landing on the UNIQUE drop table. Donators do get a drop boost here.
Normal Player: 1%
Donator: 1.1%
Super: 1.2%
Extreme: 1.3%
Legendary: 1.4%
Royal : 1.5%
Divine : 1.6%
Challenge mode adds 0.1% more per 3,000 points.
Twisted Bow, Rigour & Augury prayers have a drop rate of 1/638 from the UNIQUE table. This means that a solo-olm kill without dying would give you a drop rate of 1/6380 for each of those items (as a normal player). As an example, if you were a Legendary donator and solo-killed the olm without dying, your Twisted Bow drop rate would be 638 * (100/(1.4 * 10)) = 1/4557 - instead of 1/6380 as a non-donator.
You will always receive a drop from the DEFAULT drop table as long as you have over 3,000 Points. Every 300 points you have gives a +1% chance of receiving another DEFAULT drop (30,000+ points is a guaranteed second drop).
The Olmlet pet is only rolled if you land on a purple chest (unique drop), and then the drop rate is 1/66, so in theory, it's roughly 1/660 raids.
The Metamorphic Dust is only dropped if you finish a raid in Challenge mode, the drop rate is always 1/400 there (can be obtained without a purple chest).
Vespula's venom is rolled separately for every player with over 3,000 points, at a base rate of 1/5,000 per raid, so it does not need a purple chest. Donator rank, challenge or hard mode, the My Chamber scroll and collector's rings improve it the same way they improve the unique table chance: a Divine donator has 1/3,125. Use it on a Twisted bow to make Vespula's twisted bow.
Unique table
When you land on the UNIQUE table, one item is picked from it:
Slayer info
Combat stats
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Torva full helm
Neitiznot faceguard
Inquisitor's great helm
Serpentine helm
Amulet of torture
Amulet of blood fury
Amulet of fury
Infernal cape
Torva platebody
Inquisitor's hauberk
Fighter torso
Torva platelegs
Inquisitor's plateskirt
Blessed chaps
Ghrazi rapier
Osmumten's fang
Avernic defender
Dragon boots
Berserker ring (i)
Arclight
Armadyl helmet[1]
Void ranger helm
Blessed body
Elite void top
Elite void robe
Zaryte crossbow
Armadyl crossbow
Dragonfire ward[2]
Odium ward[2]
Dragon arrows
Ruby dragon bolts (e)
Ruby bolts (e)
Void knight gloves
Pegasian boots[1]
Ancestral hat[1]
Virtus robe top
Virtus robe bottom
Sanguinesti staff
Harmonised nightmare staff[2]
Tome of fire[3]
Elidinis' ward (f)
Arcane spirit shield[4]
Tormented bracelet
Donator: 1.1%
Super: 1.2%
Extreme: 1.3%
Legendary: 1.4%
Royal : 1.5%
Divine : 1.6%
Dexterous prayer scroll (Rigour), 
Arcane prayer scroll (Augury)
Dragon claws, 
Dinh's bulwark, 
Elder maul, 
Deadeye prayer scroll, 
Mystic vigour prayer scroll, 
Kodai wand, 
Twisted ancestral colour kit
Torn prayer scroll (Preserve)
Pk Point
Runite bar (noted)
Magic logs (noted)
Divine super combat potion(4) (noted)
Anglerfish (noted)
