Larran's key is a key obtained from killing monsters while on a Slayer task given by Krystilia. It is used to open Larran's small and big chests.
The exact odds of receiving a key scales with the monster's Combat level. For levels 1-80, the probability follows a curve between 1/1972 at level 1 to 1/100 at level 80.[1] For levels 81 or higher, the odds are between 1/99 and 1/50, scaling linearly and capping at level 350,[2] as reflected in the equation below. In addition, if players are assigned to kill slayer monsters, the drop chance is increased by 25%,[3] and any monsters killed within the Wilderness Slayer Cave have a further 15% increased chance to drop a key.[4]
The probability 
of obtaining a key when killing a monster with combat level 
is given by:
![{\displaystyle P={\begin{cases}{\frac {1}{\left\lfloor {\frac {3}{10}}\times (80-L)^{2}\right\rfloor +100}}&{\text{if }}L\in (0,80]\\{\frac {1}{\left\lfloor -{\frac {5}{27}}\times L\right\rfloor +115}}&{\text{if }}L\in (80,350]\end{cases}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/e1f6491b70177caca2122d7436f7803903061a48)
While untradeable, the killer will be able to receive the key upon killing their opponent. If the killer is an Ironman, the key will be automatically destroyed.
For an exhaustive list of all known sources for this item, see
here.
| Source | Level | Quantity |
|---|
| Abyssal demon Wilderness Slayer Cave | 124  | 1 | 1/79 |
| Ankou Wilderness Slayer Cave | 98 | 1 | 1/82 |
| Artio | 320 | 1 | 1/55 |
| Aviansie | 69–148 | 1 | 1/136–1/88 |
| Bandit | 22; 130 | 1 | 1/78 |
| Bandit (m) | 22; 130 | 1 | 1/1,109 |
| Bandit | 22; 130 | 1 | 1/90 |
| Black Heather (m) | 34 | 1 | 1/734 |
| Black Knight | 33 | 1 | 1/762 |
| Black demon Wilderness Slayer Cave | 188 | 1 | 1/68 |
| Black demon Regular | 172; 178; 184 | 1 | 1/82 |
| Black dragon Wilderness Slayer Cave | 247 | 1 | 1/59 |
| Black dragon Regular | 227 | 1 | 1/72 |
| Bloodveld | 76; 81 | 1 | 1/79 |
| Callisto | 470 | 1 | 1/50 |
| Calvar'ion | 264 | 1 | 1/65 |
| Chaos Elemental | 305 | 1 | 1/58 |
| Chaos Fanatic | 202 | 1 | 1/76 |
| Chaos druid | 13 | 1 | 1/1,446 |
| Choke devil Wilderness Slayer Cave superior | | 1 | Always |
| Crazy archaeologist | 204 | 1 | 1/76 |
| Dark warrior Low level (m) | 8 | 1 | 1/1,655 |
| Dark warrior High level | 145 | 1 | 1/87 |
| Deadly red spider (m) | 34 | 1 | 1/734 |
| Donny the lad (m) | 34 | 1 | 1/734 |
| Dust devil | 93; 110 | 1 | 1/83 |
| Earth warrior | 51 | 1 | 1/352 |
| Elder Chaos druid | 129 | 1 | 1/90 |
| Fire giant | 86; 104; 109 | 1 | 1/98 |
| Giant spider (m) | 2; 27; 50 | 1 | 1/1,925; 1/942 |
| Greater Nechryael Wilderness Slayer Cave | 200 | 1 | 1/66 |
| Greater Skeleton Hellhound (Vet'ion) | 231 | 1 | 1/62 |
| Greater abyssal demon Wilderness Slayer Cave superior | | 1 | Always |
| Greater demon Regular (m) | 92; 100; 101; 113 | 1 | 1/96 |
| Greater demon Wilderness Slayer Cave | 104 | 1 | 1/81 |
| Green dragon Regular | 79 | 1 | 1/100 |
| Green dragon Wilderness Slayer Cave | 88 | 1 | 1/84 |
| Grizzly bear (m) | 21; 42 | 1 | 1/1,144 |
| Guard Bandit (m) | 22 | 1 | 1/1,109 |
| Hellhound Regular | 122 | 1 | 1/90; 1/88 |
| Hellhound Wilderness Slayer Cave | 136 | 1 | 1/76 |
| Hill Giant | 28 | 1 | 1/911 |
| Ice giant Wilderness Slayer Cave | 67 | 1 | 1/130 |
| Ice giant Regular (m) | 53 | 1 | 1/318 |
| Ice spider | 61 | 1 | 1/208 |
| Ice warrior (m) | 57 | 1 | 1/258 |
| Jelly Wilderness Slayer Cave | 78 | 1 | 1/87 |
| King Scorpion (m) | 32 | 1 | 1/791 |
| Lava dragon | 252 | 1 | 1/67 |
| Lesser demon Regular (m) | 82; 87; 94 | 1 | 1/98 |
| Lesser demon Wilderness Slayer Cave | 94 | 1 | 1/83 |
| Magic axe | 42 | 1 | 1/533 |
| Mammoth | 80 | 1 | 1/100 |
| Moss giant Regular | 42; 48 | 1 | 1/533 |
| Nechryarch Wilderness Slayer Cave | 300 | 1 | Always |
| Pirate Pirate's Cove | 23 | 1 | 1/1,074 |
| Poison spider | 31; 64 | 1 | 1/176 |
| Porazdir | 235 | 1 | 1/70 |
| Revenant cyclops | 82 | 1 | 1/98 |
| Revenant dark beast | 120 | 1 | 1/91 |
| Revenant demon | 98 | 1 | 1/95 |
| Revenant dragon | 135 | 1 | 1/89 |
| Revenant goblin | 15 | 1 | 1/1,367 |
| Revenant hellhound | 90 | 1 | 1/97 |
| Revenant hobgoblin | 60 | 1 | 1/220 |
| Revenant imp | 7 | 1 | 1/1,698 |
| Revenant knight | 126 | 1 | 1/90 |
| Revenant maledictus | 397 | 1 | 1/89 |
| Revenant ork | 105 | 1 | 1/94 |
| Revenant pyrefiend | 52 | 1 | 1/335 |
| Rogue Level 15 | 15 | 1 | 1/1,367 |
| Rogue Level 135 | 135 | 1 | 1/89 |
| Scorpia | 225 | 1 | 1/72 |
| Scorpia's guardian | 47 | 1 | 1/426 |
| Scorpia's offspring (monster) | 15 | 1 | 1/1,367 |
| Scorpion (m) | 14; 37; 38; 59 | 1 | 1/1,406 |
| Shadow spider | 52 | 1 | 1/335 |
| Skeleton Hellhound (Vet'ion) | 194 | 1 | 1/74 |
| Skeleton Armed | 25; 45; 85 | 1 | 1/1,144–1/467 |
| Skeleton | 21–85 | 1 | 1/1,144–1/467 |
| Skeleton Unarmed | 21; 22; 60; 68 | 1 | 1/1,109–1/467 |
| Speedy Keith (m) | 34 | 1 | 1/734 |
| Spider (m) | 1; 24 | 1 | 1/1,972 |
| Spindel | 302 | 1 | 1/58 |
| Spiritual mage | 120; 121; 123; 182 | 1 | 1/72 |
| Spiritual ranger | 115–158 | 1 | 1/73–1/72 |
| Spiritual warrior | 115–158 | 1 | 1/73–1/71 |
| Venenatis | 464 | 1 | 1/50 |
| Vet'ion | 454 | 1 | 1/50 |
| Vitreous Jelly Wilderness Slayer Cave superior | | 1 | Always |
| Zombie | 13–76 | 1 | 1/1,253 |
| Zombie | 13–76 | 1 | 1/1,253–1/1,040 |
