How task chances are worked out
Every master has a list of tasks with a weight attached. When you ask for an assignment, the game drops every task you are not eligible for, then picks from what is left in proportion to weight:
chance of a task = its weight ÷ total weight of every task you can currently get
A task is removed from the pool if you lack its Slayer level, quest or other requirement, if it needs an unlock you have not bought, or if you have blocked it. Your base level is what counts; a boosted Slayer level does not unlock extra tasks. This is why the same master gives two players very different odds, and why most of what an OSRS slayer calc gets wrong comes from unlock and quest boxes left at their defaults.
Duradel is a good example. With every task available his weights add up to 327. Metal dragons (merged into one task in August 2025) carry 14, the heaviest on his list, so about 4.3% of his assignments. Abyssal demons and boss tasks sit on 12 each. Remove a few heavy tasks by blocking them and everything else gets a little more likely.
Points per task by master
No points are paid for your first four tasks. After that each master pays a flat amount, with bigger bonuses on every 10th, 50th, 100th, 250th and 1,000th task in a row: 5, 15, 25, 35 and 50 times the base.
| Master | Combat needed | Points per task | Every 10th task |
|---|---|---|---|
| Turael or Spria | None | 0 | 0 |
| Mazchna | 20 | 6 | 30 |
| Vannaka | 40 | 8 | 40 |
| Chaeldar | 70 | 10 | 50 |
| Konar quo Maten | 75 | 18 (20 with elite Kourend diary) | 90 (100) |
| Nieve | 85 | 12 (15 with elite Western Provinces diary) | 60 (75) |
| Duradel | 100 and 50 Slayer | 15 | 75 |
| Krystilia | None | 25 | 125 |
Averaged over a 50-task streak, Duradel works out at 22 to 23 points per task once the 10th and 50th bonuses are counted. Krystilia pays the most but every task is in the Wilderness. Mortimer, added in July 2026, needs 100 combat and 70 Slayer and pays a variable amount based on the task, with no streak bonuses.
Using blocks well
Each account gets up to seven block slots: one for every 50 quest points (six at 300) and a seventh from the elite Lumbridge & Draynor Diary. Blocking costs points at each master, 100 at Duradel, and unblocking is free but gives nothing back.
The block planner in the tool ranks tasks by how much removing them shifts your odds. Heavy tasks you always skip are the obvious first blocks, since each one you remove stops you paying to skip it again. The second thing to check is unlocks that add tasks. Buying a toggle that enables a task you would never do just adds weight you will end up skipping, so turn those off in the calculator and see how much better the list looks.
Sailing tasks follow the same rules. At Duradel, aquanites need 73 Sailing and the Lured In unlock, gryphons need 45 Sailing, Troubled Tortugans and the Wings Spread unlock, and frost dragons need 87 Sailing. Until you meet those requirements they simply are not in your pool.
Turning odds into a plan
The average kill count shows how long a typical task lasts, and that matters as much as the odds when you decide what to block. A rare but huge task can cost you more time than a common short one. Pair this page with our Slayer training guide for the best way to do each task, the DPS calculator to check your setup against the monster, and the Slayer money making list if you would rather keep the tasks that pay well. Boss tasks need the Like a Boss unlock (200 points) plus the boss's own requirements, and the drop chance calculator helps when you are chasing a rare drop off one. If you have not started the skill yet, the black mask is the first item worth sorting out.