The abilities of a thief are not mere human skill. They are mysterious and based in magical theory. No one who hasn’t trained in the art can hope to achieve the level of expertise of a master thief in these particular feats. The rulebook describes special (thief) abilities as requiring a turn to perform. We remove this restriction. When given a turn to perform an ability, a thief automatically succeeds. Only when the ability is performed instantly shall it require a check for a chance of failure. For example, if a thief wishes to climb his movement rate up a sheer surface, he succeeds automatically if he does so slowly (over a turn). If he wishes to sprint up a wall in one round, he makes a roll against his Climb Wall ability. These changes apply to thieves only, not to other classes with thief-like abilities (e.g. Scouts).
Open Locks
With ten uninterrupted minutes and proper tools, a thief can open any ordinary lock. If the lock must be opened in a hurry or without proper tools, a roll must be made. Failure may mean the thief must take ten minutes to open the lock, or it may mean the lock cannot be opened without proper tools.
Find, Remove and Set Traps
When coming within ten feet of trap, the GM may roll to see if the thief notices it. If the thief spends a turn carefully searching, he will always find the trap in a ten-foot area without triggering it. This is due to training and a certain intuition about how traps are designed and placed.
Once identified, most traps can be disable given another turn of work. Some traps may require certain tools. Some traps are magical and beyond the ability of a thief to disable. If the thief has an urgent need to disable a trap, he spends one round and makes a roll. If the roll is more than twice the target, the trap is triggered. Likewise, a trap can usually be reset carefully or quickly (requiring a roll).
For example, a first level thief chased by orcs. The GM rolls a 13. Thief spots a pit trap. He pauses to disable the trap. His target is 20. If he rolls 20 or lower, he notices a quick way to disable the trap, perhaps jamming a stick in a crack. If he rolls between 21 and 40, he is unable to disable the trap unless he spends a whole turn, in which case the orcs will be upon him. If he rolls 41 or greater, he triggers the trap and falls into the pit. Finally, if he does disable the trap and cross to the other side, he can spend another round trying to re-enable the trap so that the orcs might fall in themselves.
Pick Pocket or Slight of Hand
Thieves know how to take items without alerting their victims. They also know how to perform other feats that distract attention, such as tossing an item to a comrade without a guard noticing. Rarely, this feat might be performed over a turn, perhaps when stealing from a sleeper. Usually, the thief will make a roll. As described in the rules, a failure of more than twice the target also alerts the victim to the attempt.
Move Silently
Assuming a smooth floor, a thief can walk slowly in silence without much effort. No roll is necessary. Slowly means the base movement rate (e.g. 40 feet) over the span of a turn (10 minutes). This is one third the normal speed while in a dungeon. Outside, the rate is usually 40 yards over the span of a turn. Walking slowly and silently down a dungeon corridor is a great way for a thief to scout head and find traps passively.
If a thief needs to dash across a room in silence, he must make a roll. He always knows if he’s failed (unless he’s deaf!)
Listen
When moving slowly, as described with regard to moving silently or finding traps, the thief may hear interesting sounds. This is a passive ability. Listening at a door for a turn will always produce results if there’s something to hear.
If the thief only has a moment to listen, he makes a roll.
Climb Walls
Thieves can climb sheer surfaces where only the smallest of handholds exist. If the attempt made at a slow speed, the thief automatically succeeds. The thief can move is normal walking speed up a vertical surface over the course of a turn. Even overhangs and ceilings can be climbed.
If the thief needs to integrate this wall-climbing ability into combat, he must make a roll. He moves at his normal movement rate over the surface. If he fails, he slips and falls at a random point over the course. For example, if a thief attempts climbing 40 feet up a wall and fails, roll 1d4 and figure he’s moved that many feet up the wall before falling.
Hide in Shadows
When a thief hides in shadows, he melds into the shadows and stands partway between worlds. When successful, he is truly invisible to the naked eye. A genuine shadow must exist of suitable size. Standing in a flat plain at noon will offer no chance of hiding. The thin shadow of a pole is not enough. Otherwise, if none watch him, he can step into the shadows to become unseen. It does not take an entire turn.
If someone is aware of the thief, such as when combat is happening around him, he must make a roll. Failing means that hiding is impossible that round. He can try again in the next round. Even when an enemy is aware and watching the thief, he can disappear from view with a good roll. Once hidden, he can move within connecting shadows without revealing himself. When hidden this way, the thief enjoys a +4 to AC as if he were invisible, even to those with Darkvision.
Thieves can use this ability to hide themselves and then spring out the next round to perform a sneak attack. They can repeat this cycle continuously. Each time, if the thief emerges from the shadows and situates himself to the rear of an opponent, he may use his sneak attack bonus.