One of the most memorable things about previous editions of Dungeons & Dragons was, for me, the tables.
I loved the tables. As a 12-year-old, I could spend hours at the back of the 2nd Edition Dungeon Master's Guide just rolling up hordes of loot for imaginary Ancient Gold Dragons. You were using 2d10 to simulate a number from one to one hundred, and if you happened to roll that double-zero you knew you were adding something extraordinary to the loot pile.
Hand in hand with the loot tables went the random encounter tables. If PCs were travelling overland, or deigning to camp in a dungeon, or exploring some unmapped part of the city slums, the DM could get out a handful of dice and hit them with some roaming group of random nasties straight from the darkest corners of the Monstrous Compendium. Few were the heroes combing the sands of the Desert of Desolation who would expect to come face to face with 2d10 flumphs!
Okay, let's be honest - the tables were rubbish. The Deck of Many Things alone could derail a game and the 1-in-200 chance of finding it on the corpse of a random orc was a campaign-destroying timebomb waiting to go off. Having a night's sleep disrupted by 2d6 bandits or 1d3 rabid dire bears was not fun, it was tiresome.
The tables were rubbish. But they were great rubbish. 4th Edition takes them out completely, and I think that may have been a mistake.
Here is a thing about humans: we are bad at assessing probability. We do not intuitively understand long odds and we disproportionately value the unlikely. We respond illogically to random reward schedules and the knowledge that a one-in-a-billion payoff could be right around the corner will keep us buying lottery tickets in defiance of the mathematical improbability of returning a profit.
Put simply: random tables don't have to make sense. We will endure 1d3 rabid dire bears again and again in the knowledge that if the DM had rolled a 96 on that table we'd be getting a wish-granting genie. We'll keep fighting the 2d6 bandits in the hope that next time the random encounter table will deliver a modron, or a tarrasque, or an asswere, or something else that we'd never normally see in a serious campaign.
Put simply, we'll enjoy a bad idea because of the promise of a disproportionately unlikely payoff. We're dumb like that, and if being dumb means we can enjoy things that don't make sense, then it's a curse with a shiny silver lining.
So: Thunderspire Labyrinth comes with a random encounter table.
If PCs crawl around in the Labyrinth too long, or go somewhere the DM wasn't expecting, or just if the DM was feeling bored, there's a table to roll on. The module provides 10 complete level-appropriate encounters that tie into the flavour and mythos of the mountain. Better yet, each and every encounter comes with a backstory and is either the end of a side-quest or the start of one.
A treasure-seeking wight, for example, drops hints of a loot-filled minotaur graveyard (coincidentally detailed in the Dungeon Magazine side treks). A mad dwarf attempts to enlist PCs in his one-man feud with his clan. My personal favourite is a gelatinous cube attended by three wraiths - the undead are bound to their corpses, which the cube is still slowly digesting. By my reckoning, there's more story in each of these random encounters than there is the rest of the module combined.
The encounters could have been the high point of Thunderspire, and it's a shame that there's a few impediments to their use. One is the XP budget I mentioned in the last post- the biggest and meanest of these encounters gives players nearly a half-level of XP all by itself. (Speaking of which, the option of rolling randomly for these encounters was surely tongue-in-cheek - a DM who puts a level 4 party up against a level 8 random encounter is asking for an accidental party wipe.)
Another issue is that none of these encounters really tie tightly into the main plot. At best they're supplemental (and redundant) to the key areas - there's five rooms of gnolls in the Well of Demons; do we really need another two random encounters of them? At worst, they're completely tangential to what's going on in the central quest chain - it's great to hear about a distant ruin filled with treasure, but if players want to check it out, they're going to be doing it instead of the content the module had planned for levels 5 and 6, not as well as. The problem with level-appropriate content is that there's only so much of it you can do before you level.
Anyway, it's nice that the module plans for the possibility that players would rather go randomly exploring than slog through a tedious sequence of rooms filled with Duergar, but it probably would have been better off just spending the time and page space making the Duergar suck less.
I really, really love this random encounter table for its intention, for its content, and for including a gelatinous cube, and if we're going to have 4th Edition random encounter tables this is absolutely the way to do them... but ultimately it doesn't work with Thunderspire. It's asking you to make a choice - Thunderspire, or random encounters - and it's not a choice that leaves Thunderspire looking good.
 This article is entirely rhetorical; I did the maths, and then ignored it. The actual 2nd Edition chance of having a Deck of Many Things turn up in orc loot is 1 in 5,000 lairs, with no chance of finding one on a random individual. The wish-granting sort of 2nd Edition genie is either a common Efreeti or the ultra-rare Noble Djinni (representing 1% of Djinni civilisation). Both must be captured before they will grant wishes. You'll find these monsters on 0.51% of random encounters in tropical or subtropical desert, or 1.53% of random encounters occurring on the seventh level of a dungeon complex (chance of finding one on the sixth or eighth level of a dungeon = zero).