When a rogue attempts to use one of his thieving abilities, his chances of success depend on several factors: his skill, the difficulty of the task at hand, and sometimes also his luck. Each thieving task has an associated difficulty score. For example, very complex locks or traps have higher difficulty scores than simpler ones.
The method used to determine the result (success or failure) of a thieving task is different for each thieving ability.FINDING TRAPS, DISARMING TRAPS AND OPENING LOCKS
When the detect traps/illusions mode of a thief is active and there are traps within his line of sight, the game follows these steps to determine whether he detects each trap:
- Roll a d10 and adjust the result with the rogue’s luck. This means that the luck score is added to the die roll, but results higher than 10 are reduced to 10, and results lower than 1 are increased to 1. Examples:
- The luck of the rogue is 2. His die roll is 5. The adjusted result is 5 + 2 = 7.
- The luck of the rogue is 2. His die roll is 9. 9 + 2 = 11, which is higher than 10, so the result is reduced to 10.
- The luck of the rogue is -2. His die roll is 1. 1 - 2 = -1, which is lower than 1, so the result is increased to 1.
- Add the adjusted result of the roll to the Detect traps score of the rogue.
- Compare (2) with the difficulty of each trap. If (2) equals or exceeds the difficulty, the rogue detects the trap. If it’s lower, the rogue misses it.
There is a delay from the moment the thief activates the detection mode until he actually performs his first detection attempt. The duration of this delay is a random value between 0 and 6.6 seconds. After that, the game keeps performing this check once per round while the detect traps/illusions mode is active and there are traps nearby.Example: A rogue with a score of 50 in Detect traps and +2 in luck is close to two traps with difficulty scores of 55 and 60. He activates his detect traps mode. The game rolls 1d10 and the result is 4. The roll adjusted with luck is 4 + 2 = 6. The adjusted roll is added to the detect traps score, for a total of 56. 56 is higher than the difficulty of the first trap (55), but lower than the difficulty of the second one, so the rogue detects only the first trap. The rogue keeps detecting. The game rolls again, this time the result is 9. The roll adjusted with luck is 10 (9 + 2 = 11, which is reduced to 10). The adjusted roll is added to the detect traps score, for a total of 60. 60 equals the difficulty of the second trap, so the rogue detects it as well.
The same method is used to determine the result when a rogue attempts to disarm a trap or open a lock. Some locks are impossible to pick and some traps impossible to detect or disarm regardless of the skill of the thief.DETECTING ILLUSIONS AND SETTING TRAPS
The Detect illusions and Set traps abilities work in a similar way to the previous ones, but there are two important differences: The difficulty of the task is always 100, and the die rolled is a d100, which means that there is much more randomness involved.
When a rogue attempts to detect illusions the game rolls 1d100 and adds the result to his Detect Traps/Illusions score. If the result is lower than 100, the detection fails. Otherwise, the detection succeeds, all the illusion spells
within visual range of the character are dispelled, and any illusory creatures in that range are destroyed. The game keeps performing this check once per round while the detect traps/illusions mode is active and there are illusions nearby.
There is a delay from the moment the thief activates the detection mode until he actually performs his first detection attempt. The duration of this delay is a random value between 0 and 6.6 seconds. After that, the game keeps performing this check once per round while the detect traps/illusions mode is active and there are traps nearby.
Set traps works in the same way, but the die roll is adjusted with luck (see Detecting traps, disarming traps and opening locks
above). Critical failures can happen when setting traps. On a critical failure the thief gets damaged by his own trap, although the damage he receives is not the same as the damage dealt by a successfully set trap. The special snares of Bounty Hunters are not subject to critical failures. However, a score of 100 or more in Set snare means automatic success, with no chance of critical failure.STEALTH
Just like with detecting illusions and setting traps, the difficulty of stealth is always 100. The calculation, however, is more complex. The game makes this calculation:
(Hide in shadows score + Move silently score) x Environment Multiplier + (1d100 MOD luck)
- 1d100 MOD luck is the result of rolling 1d100 and adjusting the roll with luck (see Detecting traps, disarming traps and opening locks above). If the result of this adjusted roll is 1, it is a critical failure. In this case, the stealth attempt fails regardless of the skill scores.
- Environment Multiplier is a variable that depends on how well lit the place where the rogue hides is. It has three possible values: Shadows or otherwise unlighted area: 1. Indoor lighted areas: 0.67. Daylight: 0.5.
If the result of the calculation equals or exceeds 100, the stealth attempt succeeds, otherwise it fails.Critical failures
: If the result of the adjusted roll is 1, it is a critical failure. In this case, the stealth attempt fails regardless of the skill scores of the rogue. Rogues with positive luck (1 luck or higher) never get critical failures, since they cannot possibly get 1 in the adjusted roll. Rogues with neutral (0) luck have a 1% chance of critical failure. Each point of negative luck increases the chance of critical failure by 1%. For example, a rogue with -2 luck has a 3% chance of critical failure.PICKING POCKETS
When a rogue attempts to steal an item from a creature or a store, three results are possible:
- Failure: The target notices the stealing attempt and turns hostile, and the rogue doesn't manage to steal anything.
- Success: The rogue steals an item or gold.
- Nothing happens (the thief doesn't manage to steal anything, but his target doesn't notice the stealing attempt).
The chances of each outcome depend on three factors:
- The Pick pockets score of the rogue.
- The Pick pockets score of his target.
- The location of the items within the inventory of his target.
The outcome is determined in differents ways depending on whether the rogue is stealing from a store or a creature.STEALING FROM A STORE
The game makes this calculation:
(Thief skill - target skill) / 5 vs. 1d20
I. e., it calculates the difference between the Pick pockets score of the thief and the Pick pockets score of his target, divides it by 5, and compares the result with a d20 roll. If the result is equal or greater than the d20 roll, the attempt succeeds. Otherwise it fails (and the target turns hostile).STEALING FROM A CREATURE
The process is more complex when stealing from creatures. The game starts by doing the same calculation described for stores, but in this case a roll of 20 is a critical failure, i. e., the attempt fails regardless of the skill of the rogue. Just like with store stealing, if the d20 roll check fails, the attempt fails and the target turns hostile. However, if the d20 roll check succeeds, it doesn't necessarily mean that the rogue manages to steal something, it just means that his attempt goes unnoticed. The game still needs another step to determine whether he actually steals something.
Each of the inventory slots of a creature has an associated pickpocketing difficulty score. If the target has an item in an inventory slot with a difficulty score equal or lower than the Pick pockets score of the rogue, he steals that item. Otherwise you get a message informing you that the target has no items a thief of your ability can get (and nothing happens).Example: A thief with a Pick pockets score of 50 attempts to steal from a noble (Pick pockets score 0) who is wearing a ring on his finger. The game rolls a d20 and the result is 7. The first calculation ((Thief skill - target skill) / 5) yields: (50-0)/5=10. This is greater than the d20 roll, so the attempt doesn't fail. However, the pickpocketing difficulty score of worn rings (i. e., rings located in one of the ring slots of the inventory), is 60. The pickpocketing skill of the thief is lower than this, so he doesn't steal the ring. Then the thief drinks a potion of Master thievery, which raises his score to 90, and tries again. The game rolls a d20 and the result is 7 again, so he still avoids failure. This time his score is higher than the difficulty score of worn rings, so he succeeds and steals the ring.
The pickpocketing difficulty score of each inventory slot is:
- Helmet, armor, shield and boots: Cannot be stolen.
- Selected weapons and ammunition: Cannot be stolen.
- Not selected weapon: 95.
- Gloves, amulet, belt and cloak: 80.
- Rings: 60.
- Not selected ammunition and quick items: 50.
- Other inventory slots and gold: 10.
Hostile creatures cannot be pickpocketed. However, using a charm like spell to make them friendly makes them vulnerable to pickpocketing.Some conclusions
This post was originally a question about thieving abilities. I leave the original question inside the spoiler for reference:
- A rogue needs a Pick pockets score at least 5 points higher than his target just to have any chance of success at all. If the difference is lower, his stealing attempts will automatically fail.
- A rogue attempting to steal from a store has guaranteed success if his Pick pockets score is at least 100 points higher than the Pick pockets score of the seller.
- There's no way to have guaranteed success when stealing from a creature.
Each thieving ability has a score, but I don't know the meaning of those numbers. What does it mean if I have a score of 50 in opening locks? Or a score of 150 in picking pockets? What does the game do with those numbers?
Big thank you to @semiticgod
for providing all the info compiled here.