Lobstrosities are giant lobsters in the Underwater area of Fossil Island. Most weapons and shields cant be worn in the area. Weapons that can be used to kill lobstrosities include Trident of the seas/swamp and Brine sabre.
Players can stay by the bubbles around the area to prolong their stay.
Drops
100%
Item Quantity Rarity GE market price 
Raw lobster 1 Always 210
Runes
Item Quantity Rarity GE market price
Water rune 100 Common 400
Chaos rune 20 Uncommon 1,780
Nature rune 10 Uncommon 2,170
Death rune 10 Uncommon 2,030
Seeds
Item Quantity Rarity GE market price
Seaweed spore 1 Common 964
Cactus seed 1 Uncommon 98
Belladonna seed 1 Uncommon 57
Ranarr seed 1 Rare 45,466
Snapdragon seed 1 Rare 54,551
Torstol seed 1 Very rare 58,385
Herbs
The herbs dropped vary between noted and unnoted.
Item Quantity Rarity GE market price
Grimy guam leaf 1 Common 15
Grimy marrentill 1 Common 13
Grimy tarromin 1 Common 132
Grimy harralander 1 Uncommon 674
Grimy ranarr weed 1 Uncommon 7,640
Grimy irit leaf 1 Uncommon 775
Grimy avantoe 1 Uncommon 1,814
Grimy kwuarm 1 Uncommon 1,165
Grimy cadantine 1 Uncommon 1,312
Grimy lantadyme 1 Uncommon 1,391
Grimy dwarf weed 1 Uncommon 448
Other
Item Quantity Rarity GE market price
Numulite 5–14 Common 100–280
Coins 1,000 Common Not sold
Pufferfish 1 Common Not sold
Seaweed 6 (noted) Uncommon 270
Giant seaweed 6 (noted) Uncommon 2,772
Toad's legs 6 (noted) Uncommon 3,078
Caviar 2 (noted) Uncommon 480
Oyster pearls 1 Uncommon 778
Clue scroll (easy) 1 Rare Not sold
Unidentified small fossil 1 Rare Not sold
Unidentified medium fossil 1 Rare Not sold
Unidentified large fossil 1 Rare Not sold
Unidentified rare fossil 1 Rare Not sold
Rare drop table
In addition to the drops above, this monster also has access to the rare drop table.
Show/hide rare drop table Item Quantity Rarity GE market price
Coins 3,000 Common Not sold
Loop half of key 1 Common 10,307
Tooth half of key 1 Common 10,840
Chaos talisman 1 Common 505
Uncut sapphire 1 Common 455
Uncut emerald 1 Uncommon 679
Uncut ruby 1 Uncommon 1,249
Nature talisman 1 Uncommon 744
Steel arrow 150 Uncommon 4,800
Rune arrow 42 Uncommon 2,940
Rune javelin 5 Uncommon 875
Adamant javelin 20 Uncommon 1,220
Runite bar 1 Uncommon 12,368
Nature rune 67 Uncommon 14,539
Law rune 45 Uncommon 7,470
Death rune 45 Uncommon 9,135
Rune battleaxe 1 Uncommon 24,487
Rune 2h sword 1 Uncommon 37,758
Rune sq shield 1 Uncommon 22,459
Silver ore 100 (noted) Uncommon 7,000
Dragonstone 1 Uncommon 11,932
Uncut diamond 1 Rare 2,627
Dragon med helm 1 Rare 58,488
Rune kiteshield 1 Rare 32,015
Rune spear 1 Rare 11,933
Shield left half 1 Rare 65,697
Dragon spear 1 Rare 37,226
