The traditional thief class is probably the most commonly house-ruled character class—so much so that “fixing the thief ” has become something of a time-honoured tradition among rules-tweakers.
Two of the most common complaints about the thief are its percentile-based skills (a mechanic not used by any other rules subsystem) and its fixed, inflexible skill progression (must all thieves focus primarily on climbing to the detriment of all other skills at lower levels?).
This article presents an alternative system for thief skills, designed as an attempt to address these issues, with d6-based skills replacing the percentages and a simple point allocation system adding flexibility.
Thieves have the following skills: climb sheer surfaces, find or remove treasure traps, hear noise, hide in shadows, move silently, open locks, pick pockets, read languages. These skills function as described in Old-School Essentials, except that skill checks are rolled on a d6, rather than with percentile dice. The chance of success with skills is described under Expertise.
When using d6-based thief skills, usage of the following skills is modified.
The chance of success is reduced by 1-in-6 per three levels of the victim (e.g. a 6th level victim reduces success by 2-in-6). A roll of 6 means that the attempted theft is noticed. The referee determines the reaction of the victim (possibly using the reaction table under Encounters in Old- School Essentials).
Thieves have the ability to read languages from 1st level and may improve their chance of success as with all other skills— see Expertise. (Under the standard rules, thieves gain the ability to read languages at 4th level and never improve their chance of success.)
Base chance of success: All skills begin with a 1-in-6 chance of success.
Expertise points: Thieves gain expertise points to improve their chance of success with their skills. Each point allocated to a skill improves the chance of success by 1-in-6. Multiple points may be allocated to a skill, further increasing the chance of success. For example, if 2 points are allocated to a skill, the chance of success is raised to 3-in-6 (from the base 1-in-6 chance of success).
At 1st level: At character creation, a thief has 4 expertise points to allocate.
Gaining levels: A thief gains 2 additional expertise points to allocate.
Maximum chance of success: No skill may be raised above 5-in-6.