Great Olm

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. Based on old notes written in the Mount Karuulm diary, the Great Olm is implied to be the creation of a dragonkin named Karuulm,^[2] who also created the draconic creatures beneath Mount Karuulm.

During Xeric's exile and expedition of the caves in Mount Quidamortem, Olm was defeated by Xeric and his followers. Xeric succeeded in seizing power over the crystals of the caverns as he desired^[3][4], though the nature and degree of causality between those events is unclear. Xeric then sealed away the weapons and armour that the party had developed during their expedition for safekeeping.^[5]

• Basic attacks: Olm has two basic 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. Prayer reduces the damage by roughly 75-80%. Olm has a 20% chance to swap attack styles after attacking.
• 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%. The damage can be completely prevented if the player uses the corresponding protection prayer:
  • Red (sphere of aggression): Protect from Melee
  • Green (sphere of accuracy and dexterity): Protect from Missiles
  • Purple (sphere of magical power): Protect from Magic

Olm also has phase-unique attacks which can replace one of the standard 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.

• 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 afflicted 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. It is possible for Olm to fail this attack if players are standing in specific spots in the room, as it requires a certain amount of space to deploy. In failed cases, Olm will do nothing but still proceed in the attack rotation as if the attack was successful and without a catchup attack (see below).
• 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 is a 1/3 chance the Great Olm will carry out a phase-specific attack in lieu of an standard attack (provided they are not on cooldown), increasing to a 1/2 chance during the final phase of the encounter.^[6] When this roll succeeds, the Great Olm will consequently try to avoid picking any of the available phase-specific attacks it has already used in the same phase.^[7] It is still possible for Olm to use the same phase-specific attacks within the same phase despite the attempted mechanic not to do so as noted by the prior footnote.

During non-head phases, Olm has access to special attacks which only occur on a set time in his attack pattern. They are as follows:

• 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 zaps 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 possesses other characteristics that the player can encounter during a fight:

• Autoheal: During non-head phases, any attacks aimed at the head are completely healed after several ticks have passed. In the penultimate phase, the left hand 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 damage players in a 3x3 area; 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.
• Damage Mitigation: The head has 66% damage mitigation from all non-range attacks, and will heal itself if hit outside of Olm's final phase. Olm's right hand (also called mage hand) has 66% damage mitigation from all non-mage attacks. Olm's left hand (also called melee hand) has 66% damage mitigation from non-melee attacks.

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 through the barrier, it is a fight to the death. In all phases except the penultimate and final, Olm will focus on a specific set of abilities referred to as powers.

Like other bosses in the chambers, many of Olm's stats scale between its claws and head depending on the stats and amount of players in the raid, despite him having a pre-determined combat level. Monster Examine can be cast on him. In most small teams, his combat stats and max hit are comparable to God Wars Dungeon bosses. 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 being a green-coloured blast. There is a 1/5 chance the Great Olm will switch between these attack styles each time its head performs an attack.^[8] 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.

Phase-specific attacks are incorporated into the attack pattern, replacing a standard attack. Olm's attack rotation consists of the following below.

• standard attack
• empty event
• standard attack
• Crystal Burst
• standard attack
• empty event
• standard attack
• Lightning
• standard attack
• empty event
• standard attack
• Teleport
• Loops from above

Olm's standard attacks also contain a "catch-up" mechanic. If a standard attack was skipped (for instance, due to no players being in his targeted zone), Olm will attempt to "catch up" and use a standard attack on the next attack step in addition to its action for that step. This means that Olm can use a standard attack and a special attack at the same time if the prior step's standard attack was skipped. Olm will only try to catchup an attack from one step prior; skipping multiple attack steps in the rotation will not cascade into catching up multiple standard attacks. Olm will never catchup special attacks (Crystal Burst, Lightning, Teleport, Healing hand); meaning that a well-timed skip by the player can completely prevent a special attack from occurring at all.

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.^[9] 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. Falling crystals will continually fall from above until Olm is killed. As with the previous phase, he has access to all of its powers.

• The Great Olm Steam Trading Card.

• An olm is a species of aquatic serpentine salamanders living in lakes deep underground.
• Olm made a teaser appearance on the 2016 Christmas event, where it killed a worker named Ulina in a future vision.
• The Great Olm is the only monster in the Chambers of Xeric that has a defined combat level; all other monsters encountered inside do not have any known combat level.
  • In addition, its arms also have a defined combat level (though they are still part of it, so it is still technically one monster). All of Olm's attackable parts have varying combat levels.
• Despite being an NPC, Olm's parts do not appear on the mini-map.
• The Great Olm had a festive override wearing a red partyhat during the 2020, 2021, 2022, 2023, 2024, and 2025 Christmas events.
• The large hole that Olm's head pops out of changes examine text when interacted with:
  • Not present: I wonder what's down there.
  • Emerging: Whatever's down there is about to come out!
  • Emerged: Now I know what was down there.
• According to the Postbag from the Hedge #33, the Great Olm saw Xeric as a "worthy challenge" who left behind some treasures for it after taking some of his own.
• The Deep Burn attack where the player yells "Burn with me!" is a reference to Doctor Who S3:E7 "42”.
• While Olm's magic attack shares visuals with traditional dragonfire attacks, is seemingly used as inspiration for the dragon hunter crossbow, and is vulnerable to dragonbane, when asked if they are related to dragons, Olmlet states that they are olms, and suggests that they are distinctly separate enough from dragons to be offended by such a question.

v t e Dragons and dragon-like races
Chromatic dragons	Green (baby) (brutal) Blue (baby) (brutal) Red (baby) (brutal) Black (baby) (brutal)
Metal dragons	Bronze Iron Steel Mithril Adamant Rune
Slayer monsters	Wyrm (Shadow) (Wyrmling) Lava Strykewyrm (Magma) Long-tailed Wyvern Spitting Wyvern Taloned Wyvern Skeletal Wyvern Brutal black Ancient Wyvern Drake (Guardian) Hydra (Colossal) (Alchemical)
Other	Lava Frost Reanimated Revenant Crystalline Corrupted Fairy Colossal Wyrm Bosses Elvarg Galvek Great Olm King Black Dragon Vorkath The Hueycoatl NPCs Alvarg Hekala K'klik Mr. Mordaut Dragonkin Dragonkin (A Tail of Two Cats) Dragonkin (Dragon Slayer II) Forcae Garak Karuulm Kerapac Orthacas Sakirth Sithaph Skeka Strisath Zorgoth
Related	Merodach

v t e Bosses
World bosses	The Hueycoatl Scurrius Giant Mole Deranged archaeologist Sarachnis Kalphite Queen Corporeal Beast Gemstone Crab The Barrows Brothers Ahrim the Blighted Karil the Tainted Dharok the Wretched Guthan the Infested Torag the Corrupted Verac the Defiled The Dagannoth Kings Dagannoth Prime Dagannoth Rex Dagannoth Supreme God Wars Dungeon Kree'arra Commander Zilyana General Graardor K'ril Tsutsaroth Nex Moons of Peril Eclipse Moon Blue Moon Blood Moon The Wilderness bosses Revenant maledictus Chaos Fanatic Crazy archaeologist Scorpia King Black Dragon Chaos Elemental Vet'ion (Calvar'ion) Venenatis (Spindel) Callisto (Artio)
Instanced bosses	Amoxliatl Brutus (Demonic) Royal Titans (Branda the Fire Queen) (Eldric the Ice King) Zulrah Vorkath Phantom Muspah The Nightmare (Phosani's Nightmare) Yama Doom of Mokhaiotl Maggot King Mad Angel Sporadic bosses Obor Bryophyta The Mimic Hespori Skotizo The Forgotten Four The Leviathan The Whisperer Vardorvis Duke Sucellus
Slayer bosses	Shellbane gryphon Grotesque Guardians (Dusk) (Dawn) Abyssal Sire Kraken Cerberus Araxxor Thermonuclear smoke devil Alchemical Hydra
Minigame bosses	Crystalline Hunllef Corrupted Hunllef TzTok-Jad TzKal-Zuk Sol Heredit
Skilling bosses	Tempoross Wintertodt Zalcano
Raids	Chambers of Xeric Tekton Vanguard Vespula Vasa Nistirio Muttadile Great Olm Theatre of Blood The Maiden of Sugadinti Pestilent Bloat Nylocas Vasilias Sotetseg Xarpus Verzik Vitur Tombs of Amascut Akkha Ba-Ba Kephri Zebak Tumeken's Warden Elidinis' Warden

v t e Chambers of Xeric
Mount Quidamortem	Captain Rimor Gnosi Historian Duffy Mountain Guide Natural Historian Stuliette
NPCs (inside)	Regular Cave snake Creature keeper Corrupted scavenger Scavenger runt (removed) Scavenger beast Guardian Jewelled Crab Ice demon Lizardman shaman Skeletal Mystic Deathly ranger Deathly mage Bosses Vasa Nistirio (Glowing crystal) Tekton Vespula (Lux grub) (Vespine soldier) (Abyssal portal) Vanguard Muttadile (Meat tree) Great Olm
Scenery	General scenery Ancient chest Bank chest Chest Score board Bubbles Ice storm Energy well Boulder Rotten sapling Rocks Magical fire Fire Giant Anvil Trough Brazier Shimmering barrier Tightrope Sapling Magical fire Herb patch Noxious tendrils Septic tendrils Spirit tendrils Old tools Gourd tree Weeds Mystical barrier Storage units Tiny Small Medium Large Massive
Items	Fish Pysk (raw) Suphi (raw) Leckish (raw) Brawk (raw) Mycil (raw) Roqed (raw) Kyren (raw) Burnt Bats Guanic (raw) (creature) Prael (raw) (creature) Giral (raw) (creature) Phluxia (raw) (creature) Kryket (raw) (creature) Murng (raw) (creature) Psykk (raw) (creature) Burnt Herblore Seeds Golpar Buchu Noxifer Herbs Golpar (grimy) Buchu (grimy) Noxifer (grimy) Ingredients Endarkened juice Stinkhorn mushroom Cicely Potions Weak Elder (-) Twisted (-) Kodai (-) Antipoison (-) Revitalisation (-) Prayer enhance (-) Xeric's aid (-) Overload (-) Standard Elder Twisted Kodai Antipoison Revitalisation Prayer enhance Xeric's aid Overload Strong Elder (+) Twisted (+) Kodai (+) Antipoison (+) Revitalisation (+) Prayer enhance (+) Xeric's aid (+) Overload (+) Texts Creature keeper's journal Nistirio's manifesto Tekton's journal Transdimensional notes Vanguard judgement Houndmaster's diary Dark journal Miscellaneous Kindling Empty gourd vial (water-filled) Keystone crystal Cave worms Cavern grubs Medivaemia blossom Mallignum root plank
Rewards	Equipment Dragon claws Elder maul Dragon hunter crossbow Twisted bow Twisted buckler Kodai wand (insignia) Dinh's bulwark Ancestral robes Hat Robe top Robe bottom Prayer scrolls Torn Dexterous Arcane Other Dark relic Ancient tablet Olmlet Challenge Mode Twisted ancestral kit Colour kit Hat Robe top Robe bottom Pet transmogs Metamorphic dust Puppadile Tektiny Enraged Tektiny Vanguard Vasa Minirio Vespina Flying Vespina Capes Xeric's guard Xeric's warrior Xeric's sentinel Xeric's general Xeric's champion