Thief Ability Redux: Piles of Dice

Riffing on Hill Canton's post on thieves yesterday (or whenever, given the incubation period of posts around here, it may well be December of 2176 before these pixels see the light of day) I decided to post my own rant on thief abilities.

What are the odds, buddy?

One of my many grievances with thief abilities is that success is almost never influenced by conditions. That is, no matter how well concealed the trap is or how alert/inert the guards are, your chance of detecting it or bypassing them remains the same.* Sure, the DM can modify a trap or lock and say "your -20 to open it" or whatever, but it's so specific and granular that it becomes a nuisance and only dickheads ever use this method except in the odd extreme circumstance.

In an ideal world, conditional difficulty should be part of the system so the DM doesn't feel like s/he's rewording the Old Testament just so that the lock to the crypt can be a little tougher to open than the lock on your sister's diary.  It should be easy for the DM to assess difficulty without taking a lot of time, rather than trying to decide whether it's a -22% penalty or a -24% penalty, it should be broad enough that the DM can make a decision quickly and we can all get to the matter at hand: slaughtering orcs and stealing their treasure.

So...
Here's how it goes: the thief (or the Maestro del Dungionni, depending on the circumstances) rolls d20 and a pile of six-siders at the same time.  If the 20 sider + thief's level are equal to or greater than the total of the pile of 6'ers: Success! How many six siders in a pile, you ask? Good question: depends on how difficult the DM feels the challenge is. Here's a handy table to use as a guideline:

Table IX.A.2.d(17): Dice Piles and Difficulty of Thieving Abilities

			Avg. Success Rate for a Thief of:
Dice Pile	Difficulty Rating	Description	1st Level	5th Level
1d6	Super easy	Fail this and you're out of the Guild	92%	95%**
2d6	Easy	Only a newb would screw this up	75%	92%
3d6	Modestly difficult	Still, you better succeed if you want  to earn your keep	58%	77%
4d6	Difficult	We have faith in you!	40%	60%
5d6	Pretty Difficult	You might as well give it a try...	24%	43%
6d6	Very Difficult	Better have a Plan B just in case	11%	26%
7d6	Fat Chance	Give us a minute to back up a ways before you try that	4%***	13%

Pretty fancy, right?

Some guidelines on how I'd adjudicate this:****

Picking a lock on a typical dungeon door: 3d6
Picking a lock to the King's treasure room: 5-7d6, depending on the wealth of the king and his security measures
Sneaking past a guard who's chatting with his buddy about the Misfits show he went to last night: 2d6
Sneaking past a guard who's on high alert: 4d6
Sneaking past a guard who just saw you a minute ago and knows that you're trying to sneak past him: 6d6
Climbing a craggly wall with ample hand/foot holds: 1 or 2d6
Climbing a rough hewn yet slick wall: 3 or 4d6
Climbing a sheer, polished, monolithic wall: you're a thief not Spiderman.

... and so forth

Some of you who are more statistically gifted than I are probably thinking "Why not just tell the dudes they've got a 75% chance to defuse an Easy bomb or 40% chance of deciphering a Difficult language or whatever?" You could do this if you have a good idea of the odds of success for every thief ability under a wide variety of circumstances. I don't have that info handy, nor do I trust myself to make up reasonable odds for such on the fly.

The beauty of the Pile o' Dice system is that as a DM I don't have to think very granularly about the odds of success, I let the dice do the dirty work. Yes, on average a 1st level thief has a ~58% chance of hiding in a 3d6 shadow, fine.  But, as DM, I don't actually have to say that.  Instead, I'm saying "your odds are somewhere between 20% and 95%, but are most likely somewhere in the middle, so let's just see what happens here..." This is probably just my laziness but I find it much easier to assign a range of probability than a single, precise value.



* The exception here being picking pockets of leveled characters, of course. Which clearly was a reaction to those dickhead players who insist that it is their thief's moral obligation to steal from his colleagues mid-dungeon, yet get indignant when their moronic character finds himself hogtied and naked while his erstwhile colleagues offer his carcass to a band of gnolls in exchange for free passage through their domain.  
** Assumes 1 is a fumble, otherwise 100% chance of success
*** 5% if you abide by the 20 always succeeds rule.  I know, I'm being inconsistent here.
**** I loathe the word adjudicate as used by gamers--though I don't deny it's usefulness. Still, I hope you appreciate the personal pain I am subjecting myself to in order to deliver this post to you.