Lobstrosity | OSRS Index

Lobstrosity



Released		7 September 2017 (Update)
Members		Yes
Combat level		68
Size		3x3
Examine		An extremely vicious lobster type thing.

Combat info

XP bonus		+0%
Max hit		9
Aggressive		Yes
Poisonous		No
Attack style		Stab
Attack speed		4 ticks (2.4 seconds)
Respawn time		25 ticks (15 seconds)

Slayer info

Slayer level		None
Slayer XP		50 xp
Category		Scorpions
Assigned by

Combat stats


50	60	80	40	1	1

Aggressive stats


+0	+0	+0	+0	+0	+0

Melee defence


+30		+50		+15

Magic defence


+99			25% weakness

Ranged defence


+70		+70		+70

Immunities

Poison		0% resistance
Venom		0% resistance

Open in DPS calculator
Advanced data

Monster ID		7796
Link		MOID

Lobstrosities are giant "lobster-type thing[s]" located in the south-east corner of the Underwater area of Fossil Island. Most weapons and shields cannot be equipped in this area. Weapons that can be equipped and used to kill lobstrosities include the dragon harpoon, merfolk trident, trident of the seas/swamp, brine sabre, and magic secateurs. Lobstrosities may also be killed with magic. It is recommended to bring a herb sack with you as these drop many useful herbs.

A fishbowl helmet cannot be worn in this area, but players can easily use the nearby air bubbles to replenish oxygen while fighting lobstrosities.

Lobstrosities can be safespotted with magic from the south-western corner of the south-eastern bubble.

Seaweed spores will spawn around the area randomly.

Locations

Location	Levels	Members	Spawns	Map	League region
Underwater area of Fossil Island	68		9	Show map	Misthalin✓

Drops

Drop rates are estimated based on 214,390 samples from the Drop Rate Project, unless otherwise cited.

The average Lobstrosity kill is worth 1,268.9.

100%

	Item	Quantity	Rarity	Price	High Alch
	Raw lobster	1	Always	110	42

Runes

Item	Quantity	Rarity	Price	High Alch
Water rune	100	8/118	500	200
Chaos rune	20	8/118	2,120	1,080
Death rune	10	5/118	1,850	1,080
Nature rune	10	6/118	1,710	1,080

Herbs

2 herbs are dropped at a time, and can be of different types.

Item	Quantity	Rarity	Price	High Alch
Grimy kwuarm	1	2 × 15/944	1,814	12
Grimy cadantine	1	2 × 3/236	2,076	13
Grimy lantadyme	1	2 × 9/944	1,232	13
Grimy dwarf weed	1	2 × 3/326	1,343	14

Standard herb drop table

There is a 14/118 chance of rolling the herb drop table. 2 herbs are dropped at a time, and can be of different types.

Item	Quantity	Rarity	Price	High Alch
Grimy guam leaf	1	1/33.7	189	7
Grimy marrentill	1	1/45	185	8
Grimy tarromin	1	1/59.9	120	9
Grimy harralander	1	1/77.1	284	9
Grimy ranarr weed	1	1/98.1	5,262	18
Grimy irit leaf	1	1/134.9	1,258	10
Grimy avantoe	1	1/179.8	1,341	10
Grimy kwuarm	1	1/215.8	1,814	12
Grimy cadantine	1	1/269.7	2,076	13
Grimy lantadyme	1	1/359.6	1,232	13
Grimy dwarf weed	1	1/359.6	1,343	14

Seeds

There is a 4/118 chance of dropping 2 seeds from the Uncommon seed drop table, and a 5/128 chance of dropping 1 seed from the Rare seed drop table.

Item	Quantity	Rarity	Price	High Alch
Seaweed spore	5	6/118	1,015	60
Limpwurt seed	1	1/225.7	15	7
Strawberry seed	1	1/236	7	10
Marrentill seed	1	1/247.3	17	1
Jangerberry seed	1	1/336	5	36
Tarromin seed	1	1/363.7	12	1
Wildblood seed	1	1/372.5	81	8
Watermelon seed	1	1/490.7	234	33
Harralander seed	1	1/552.1	32	2
Snape grass seed	1	1/772.9	15,101	56
Ranarr seed	1	1/792.7	28,028	30
Whiteberry seed	1	1/909.3	6	79
Mushroom spore	1	1/1,066.1	106	51
Toadflax seed	1	1/1,145	979	6
Belladonna seed	1	1/1,717.6	108	106
Irit seed	1	1/1,717.6	72	3
Poison ivy seed	1	1/2,378.2	13	99
Avantoe seed	1	1/2,576.3	356	4
Cactus seed	1	1/2,576.3	48	59
Kwuarm seed	1	1/3,435.1	2,003	6
Potato cactus seed	1	1/3,864.5	9	84
Snapdragon seed	1	1/6,183.2	43,773	36
Cadantine seed	1	1/7,729	5,135	4
Lantadyme seed	1	1/10,305.3	113	5
Dwarf weed seed	1	1/15,458	690	3
Torstol seed	1	1/30,916	15,463	42
Toadflax seed	1	1/119.1	979	6
Irit seed	1	1/173.8	72	3
Belladonna seed	1	1/179.9	108	106
Poison ivy seed	1	1/249.7	13	99
Avantoe seed	1	1/254.7	356	4
Cactus seed	1	1/268	48	59
Potato cactus seed	1	1/367.5	9	84
Kwuarm seed	1	1/372.8	2,003	6
Snapdragon seed	1	1/559.2	43,773	36
Cadantine seed	1	1/803.9	5,135	4
Lantadyme seed	1	1/1,118.4	113	5
Snape grass seed	3	1/1,286.2	45,303	168
Dwarf weed seed	1	1/1,837.4	690	3
Torstol seed	1	1/2,858.2	15,463	42

Other

Item	Quantity	Rarity	Price	High Alch
Coins	1,000	9/118	1,000	1,000
Pufferfish	1	8/118	Not sold	138
Giant seaweed	6 (noted)	8/118	582	6
Seaweed	6 (noted)	8/118	30	6
Toad's legs	2 (noted)	6/118	518	2
Caviar	2 (noted)	5/118	142	60
Oyster pearls	1	4/118	643	840

Gem drop table

There is a 3/118 chance of rolling the gem drop table.

Item	Quantity	Rarity	Price	High Alch
Nothing	N/A	1/78.81; Never^{[d 1]}	N/A	N/A
Uncut sapphire	1	1/157.33; 1/79.9^{[d 2]}	228	15
Uncut emerald	1	1/314.67; 1/159.79^{[d 2]}	473	30
Uncut ruby	1	1/629.33; 1/319.58^{[d 2]}	1,087	60
Nature talisman	1	1/1,678.22; 1/852.22^{[d 2]}	268	2
Uncut diamond	1	1/2,517.33; 1/1,278.33^{[d 2]}	2,439	120
Rune javelin	5	1/5,034.67; 1/2,556.67^{[d 2]}	675	1,200
Loop half of key	1	1/5,034.67; 1/2,556.67^{[d 2]}	9,756	60
Tooth half of key	1	1/5,034.67; 1/2,556.67^{[d 2]}	9,887	60
Rune spear	1	1/80,554.67; 1/4,793.75^{[d 2]}^{[d 3]}	11,599	12,480
Shield left half	1	1/161,109.33; 1/9,587.5^{[d 2]}^{[d 3]}	65,355	66,000
Dragon spear	1	1/214,812.44; 1/12,783.33^{[d 2]}^{[d 3]}	38,438	37,440

^ The "nothing" drop is removed while wearing a ring of wealth.
^ ^2.00 ^2.01 ^2.02 ^2.03 ^2.04 ^2.05 ^2.06 ^2.07 ^2.08 ^2.09 ^2.10 The drop rate is increased while wearing a ring of wealth due to the "nothing" drop being removed.
^ ^3.0 ^3.1 ^3.2 Only dropped if Legends' Quest has been finished; if not, a talisman is dropped instead.

Tertiary

Item	Quantity	Rarity	Price	High Alch
Numulite	5–14	45/175	190–532	150–420
Unidentified small fossil	1	5/350	Not sold	60
Unidentified medium fossil	1	5/700	Not sold	120
Unidentified large fossil	1	5/875	Not sold	180
Unidentified rare fossil	1	5/3,500	Not sold	750
Clue scroll (easy)	1	1/128^{[d 1]}^{[d 2]}^[1]	Not sold	12

^ The easy clue scroll drop rate increases to 1/121 after unlocking the easy Combat Achievements rewards tier.
^ Clue scrolls will drop as scroll boxes after the completion of X Marks the Spot.

Changes

Date	Changes
27 August 2025 (Update)	Lobstrosities now drop unnoted herbs instead of noted.
25 June 2025 (Update)	Lobstrosities now have a 25% elemental weakness to earth spells.
12 July 2018 (Update \| poll)	Lobstrosities now drop a maximum of 5 seaweed spores instead of 1.

Trivia

Lobstrosity could be a reference to The Dark Tower series by Stephen King where creatures of the same name appear in the second book, The Drawing of the Three.

References

^ Jagex. Mod Tide's Twitter account. 24 May 2019. Archived from the original on 24 May 2019. Mod Tide: "I know its been a while since the clue expansion but here is the information on clue scroll drop rates and loot chances! If anything changes I will keep you posted."

Fossil Island

Museum Camp

	Fossil Storage Fossil Island bank Fossil Island General Store Notice board
NPCs	Charles David Dog Fossil Collector Jardric Peter John John Mattimeo Petrified Pete Shop keeper
Items	Fossil Island fossils Numulite
Scenery	Broken spinning wheel ^(built) Chest pieces (Fossil Island) ^(built) Fire pit ^(built) Half-built Loom ^(built) Ring of Stones ^(built) Table parts ^(built)

Mushroom Forest

	Mycelium pool Wyvern Cave
NPCs	Ancient Zygomite Irene Herbiboar Maz Squirrel Weve Ammonite Crab
Items	Pyrophosphite Calcite

Tar Swamp

	Bellshroom Sulliuscep Spine mushroom
NPCs	Hoop Snake Charles Charlington Tar Monster Deranged archaeologist
Items	Hoop snake Sulliuscep cap Uncooked mushroom pie Mushroom pie Breadcrumbs Archaeologist's diary Steel ring

Fossil Island Volcano

	Volcanic Mine Petrified Pete's Ore Shop
NPCs	Lava beast Petrified Pete
Items	Soda ash Volcanic ash Volcanic mine teleport Calcite Pyrophosphite Iron ore fragment Silver ore fragment Coal fragment Gold ore fragment Mithril ore fragment Adamantite ore fragment Runite ore fragment Large rock Ash covered tome Heat-proof vessel Ore pack Dragon pickaxe (broken)
Scenery	Ash pile Boulder (Volcanic Mine)

Underwater

	Mairin's Market Pile of Fishbowls Plant door Clam Chest Hole
NPCs	Mernia Mairin Ceto Annette Puffer Fish Harlequin Fish Paradise Fish Red Fantail Fish shoal Lobstrosity
Items	Mermaid's tear Glistening tear Pufferfish Drift net Merfolk trident Seaweed spore Bowl of fish

House on the Hill

	Mycelium Transportation System Stone chest Strange Machine Strange blocks Strange stone
NPCs	Skeka
Items	Ancient wyvern shield Small enriched bone Medium enriched bone Large enriched bone Rare enriched bone Fossil island note book Ancient diary

Other

Wilhelm

Music

Source site	Old School RuneScape Wiki
Canonical source	Lobstrosity
Content license	CC BY-NC-SA 3.0
License status	declared
Picture	Lobstrosity · file details