It doesn't get more old school than rolling a d6 to check for wandering monsters in a dungeon. In the early 1980s, rolling a "1" meant you were in for a fight. Back then, you could even acquire dice which replaced the "1" with a monstrous face: like the Flying Buffalo "Death Dice" (above left), or Lou Zocchi's Gamescience "Demon/Orc Dice" (right). But the very first dungeon delvers encountered wandering monsters when the die came up "6" -- the rule shifted to encounters resulting from a "1" around the time these two dice appeared. Read on for a bit more about dice in this tradition, and the change in the wandering monster rules that went along with them.
The Flying Buffalo "Death Dice" seem to have appeared shortly after the fifth edition of the Tunnels & Trolls rules -- you can find them advertised in the January 1980 Flying Buffalo catalog that shipped in fifth edition boxed sets:
Now, from its first edition in 1975 up until its fifth, T&T had followed the rule that, "At the beginning of each turn, the D.M. rolls 1 die -- if he gets a 6, he springs a W.M. [wandering monster] or three on the lucky people." That text is a loose paraphrase of the original 1974 Dungeons & Dragons language, which read: "At the end of every turn the referee will roll a six-sided die to see if a 'wandering monster' has been encountered. A roll of 6 indicates a wandering monster has appeared." This high-roll-means-monsters precedent would inform random encounter rolls for the next several TSR games: Empire of the Petal Throne and Metamorphosis Alpha would both follow it, as would the Holmes Basic Set in 1977.
Other early non-TSR role-playing games like Bunnies & Burrows and Traveller also stipulated that high rolls on a d6 led to random encounters. All these rules ultimately derived from Avalon Hill's Outdoor Survival requirement that players roll a die at the end of their turn: "if you roll a 5 or 6 you must play the Wilderness Encounter chart," which in that game could mean stumbling into the maw of a hungry predator.
But the 1979 fifth edition of T&T abruptly reversed the guidance, stating that "At the beginning of each turn the GM rolls one die - if a 1 comes up, he springs a wandering monster or three." And by the time the Moldvay Basic Set revised the Holmes set early in 1981, D&D agreed: it instructs referees to "roll 1d6: a result of 1 indicates the party will encounter a Wandering Monster in the next turn." So... when did the roles of 1 and 6 become reversed, and why?
One early place we see a 1 resulting in a random encounter offers us a clue: that is the Realm of Yolmi (1977), an obscure game which used a d8 for wandering monsters:
The use of dice other than a d6 for random encounter checks made the number 6 lose some of its luster, as it was no longer at the upper bound of what you could roll on a d8, a d12, or a d20. But the lower bound for all those dice remained constant at 1. If we look ahead to the summer of 1978, the Steading of the Hill Giant Chief (G1) D&D module shows wandering monster checks that also depend on rolling a 1 on a d8 or a d12:
... and this was surely the motivation for the AD&D rule as it appears in the 1979 Dungeon Masters Guide, namely that "When an encounter check is indicated, roll the appropriate die, and if a 1 results, an encounter takes place." If we had to assign any single marker to the place where the rule firmly switched to rolling 1s, it would be here. The "appropriate die" varied based on the environment checked for potential encounters; in the dungeon, as the example DMG dungeon crawl shows us, "the DM rolls a d6 to see if a 'wandering monster' appears." This is surely what drove Moldvay to override the guidance on d6 wandering monster rolls in Holmes. And Lou Zocchi's "Demon/Orc" dice were just made for this rule, when they came on the scene late in the spring of 1980:
Probably the widespread association of high rolls being good and low rolls being bad, with a 1 especially signifying a critical fumble, helped steer play at the tabletop in this direction -- though the current edition of D&D has gone back to favoring high rolls (on a d20) leading to random encounters. But back in the early 1980s, there was a substantial market for d6s decorated for the dramatic revelation of an encounter to come, so much so that in 1981, Zocchi followed up with his "Destiny Dice" d6s with a skull and crossbones in place of the 1:
As with Zocchi's "Demon/Orc Dice," the image wore off easily, leaving some barely recognizable today. But they are still perfect for adding a bit of early-80s flavor to any gaming table. And they inaugurated a tradition of dice made especially for role-playing games which substitute out the traditional numbers on a face for images, sometimes with system effects.
Previously: Identifying 1970s Polyhedral Gaming Dice