From DnD B/X it is a small step to the Original Version of 1974, alternatively called Little Brown Books or colloquially “0e”. The difficulty is that the original 3 booklets assumed gaming experience at wargaming tables. They were a product by fans of tabletop battle games for other fans of tabletop battle games, and did not expect to find any interest outside of a certain circle. But they did, quickly, and their gaps have been quickly amended with an assortment of additions and partially reference back to Chainmail.

Various Zine articles also clarified ambiguities, added things or changed things, leaving the state of the scattered rules in such a state that it was obviously needed to make a Holmes, later Moldvay, and later Mentzer version to get things back on track and allow normal players, people who did not spend their days hunting for explanations in various places, to play and enjoy the game with a more common understanding.

The Original Rules are primarily a medium of inspiration and trust: If in doubt, ask the Game Master how things are. If no rule for a situation is present, make one up.

More recently, a variety of enterprising gamers who agreed with Tom Moldvay’s statement have tried to collect the important bits and pieces of 0e D&D and make a version of the “original” rules that can stand alone and revive the original spirit across various desks and playing groups.

Delving Deeper

One beautiful and, if people who know a lot about the topic are to believed, particularly faithful interpretation of a particularly good selection of original materials, including Chainmail and including the (optional) Thief class, is “Delving Deeper” by Immersive Ink.

Given the wide range of source material, there are several bits of differences that can be argued and come to fisticuffs about, notably

• the differences in Hit Dice of the Fighter class,
• or the difference in spell lists,
• or that Delving Deeper builds on the basis of ODnD to go farther, like by measuring encumbrance in lbs instead of coin, and also by having STR have an impact on how much you can carry. In the original rules, everybody was the same, a measly bookworm and a hardy fighter both got encumbered down to half movement at 1500 to 3000 coin. Delving Deeper lets Hercules carry double the weight of hungry Louie, and halves movement at 100-150 lbs for a weakling and at 200-300 lbs for a strongman. A slight deviation, but one that places the Original load in the bandwidth of average to strong characters, which is sensible.
• For calculating prime requisites, Original DnD has some calculations of various attributes, while DD simplifies this and declares every 2 points of wisdom to raise any prime requisite for the purpose of calculating XP bonuses.
• DD gives characters with a constitution score of 3-6 at least a 20% chance to survive system shock, while ODnD did not give them any.

So they are not exactly the same; but on most issues they go hand in hand without conflict, and Delving Deeper represents, without doubt, one of the most faithful and most useful “clones” of the “0e” Original Dungeons & Dragons, and where it differs from the original, it does so in a useful and constructive way.

Different Thieves

The more important difference – Thief skills – is that Original DnD from supplement Greyhawk gives the Thief this advancement table, where climbing sheer surfaces starts at 88% and rises to 100% skill, while moving silently starts at 20% and rises in 5% increments, also to 100% at level 12, etc. Other versions like B/X or BECMI or Advanced D&D have their own tables for this skill progression.

Delving Deeper veers of that general consensus and lets the thief just do all his skills at a throw of 3-6 on a d6. This means, in DD the thief starts already very competent and stays that way, while in regular D&D they start as newbies and slowly grow to become untouchable masters of their craft.

Learn = Do

So I tried it, played it in an online campaign first, then offered to start a campaign to players, and finally started to GM another Delving Deeper campaign of my own for a group of kids.

But I am no expert with lifelong D&D track record, I am just an interested player. So I will let you have a look for yourself. Here are the rules for you to compare with Original 1974 D&D and come to your own conclusions about the merits of Delving Deeper:

http://ddo.immersiveink.com/dd.html

Sword & Spell – even more faithful to the Original RAW

Another “clone” of Original Dungeons & Dragons that I have encountered is organised in 3 little booklets (coincidence?) that are called “Might & Magic, Underworld & Wilderness Adventures, and Monsters & Treasures, and are collected under the title “Sword & Spell”, by a company called “OSR Hobbies”. I have struggled to find the differences between that and Original D&D as written, and I have not found them yet. What is the special thing about this “Sword & Spell” retroclone if it does not differ from the 0e at all? — presentation.

“Sword & Spell” tries to organise the ODnD rules in a shorter, more concise way, with clearer wording, and with moving rules-explanations, which are found a bit after the fact in the Original ODnD rules, right up to the topic they belong to. They are small and concentrated 0e with no deviation from the LBBs, as far as I could determine (which also means, there is no Thief). I am not yet convinced that there really is no rules-deviation, especially as they name Gygax and Arneson as “inspiration”, not as hard source. But so far I failed to identify any rules difference.

— edit: According to the creator, some slight changes are present, owing to implied rules from Chainmail 2nd edition (1972) being spelled out; for example, the paralyzing effect of the wight or wraith is spelled out as “through fear”, as it would be in Chainmail, instead of a presumed result of the wound, as it is implied in later versions…. but that changes nothing about the effect.
So yes, “Sword & Spell” is faithful ODnD.

The “Sword & Spell” booklets cost money, though, while Delving Deeper is a labour of love that is provided without recompense for the creator.

You can find it on DrivethruRPG.