I was inspired by the Pyrologist character class for OD&D (starts on page 3, though not all of it is readable) and did some number-crunching.  It's surprisingly easy to backport character classes from 3.5 to OD&D.  BAB/1.5 becomes the to-hit bonus, roll the hit dice down by one level to a minimum of d4, and only keep special abilities if they're thematic enough and the character gains them at first level.  So Cleave, Turn Undead, and Backstab/Sneak Attack for the Fighter, Cleric, and Thief/Rogue, respectively.

In the end I decided to convert 3 additional classes, which I may or may not let my players use: the Dread Necromancer, the Beguiler, and the Warlord.  I like the spell selection, though all three are spontaneous casters and I'm not sure if I'll keep that element or make them traditional spellcasters.  If I do let the players take those classes, it will only be after they've encountered an NPC of that class.  Much more fun to hit them with an Orb of Acid when they have no idea something like that is possible.  

At the very least, it'll be a good source of new spells for any spellcasters in the party (assuming they can get their hands on the spellbook).

I'm also thinking of creating a sort of hedge mage who can only cast spells from a specific domain, one spell from each level.  "Watch out for those holly berries!  They explode!"  "Riiiight..."  *BOOM!*

Are you doing this for a campaign, or an experiment, or what? And are you looking for reactions or suggestions?

I'd say that it's a perfectly reasonable idea. New classes started coming into OD&D almost immediately, there's no reason that a 3.5 class is more or less reasonable an addition than what was added. Mixing up the spell lists like with beguiler and dread necromancer is a reasonable way to tailor your spellcasters--much like druids, and in AD&D illusionists (or was there an OD&D illusionist in one of the magazines? I forget).

Dunno.  Honestly, I spend a lot of time cobbling together new rules systems based on Fudge, and I just managed to create a conversion system from OD&D to Fudge, so naturally I've started spending time messing around with OD&D systems.  I talk about players, but I don't currently have anybody I'd be running this for.  Mostly a thought-experiment.  Just throwing it out there and seeing if anybody has any feedback.  *shrug*

EDIT: Although I do have a minor concern about one thing.  In some editions, wizards normally get all their first level spells then pick up higher level spells elsewhere.  If we have two spellcasters with different spells, what's to keep them from teaching each other all their first level spells and potentially doubling their spells known?

I've done a bunch.

OTOH, I thought the whole point of playing OD&D was that it's supposed purity, unsullied by the hands of man, only the god Dave Arneson, as channeled by his prophet EGG.

Quote from: JeremyR;1015704I've done a bunch.

OTOH, I thought the whole point of playing OD&D was that it's supposed purity, unsullied by the hands of man, only the god Dave Arneson, as channeled by his prophet EGG.

Nope.  In my case it's all about the simplicity.  Once RPG rules pass a certain point I have trouble understanding them, so I want to work with the absolute simplest version of D&D that can still be called D&D.  Even then, I surprised myself when I realized I could understand the rules given in the Swords and Wizardry whitebox edition.

And let's be honest here: nobody plays OD&D strictly by-the-book, because the book itself requires interpretation and encourages house-ruling.

Quote from: abcd_z;1015711Nope.  In my case it's all about the simplicity.  Once RPG rules pass a certain point I have trouble understanding them, so I want to work with the absolute simplest version of D&D that can still be called D&D.  Even then, I surprised myself when I realized I could understand the rules given in the Swords and Wizardry whitebox edition.

I love OD&D for the simplicity as well, and I've ported some 3E ideas into my OD&D campaigns. When I make new OD&D classes (from any source) I use the base OD&D classes as a starting point in terms of hit dice and attack numbers and so on, then add in bonus powers, etc., to create the effect I like.

I like the way this thread is shaping up so far.

Quote from: JeremyR;1015704I've done a bunch.

OTOH, I thought the whole point of playing OD&D was that it's supposed purity, unsullied by the hands of man, only the god Dave Arneson, as channeled by his prophet EGG.

There's no purity in anything, TTRPGs are no exception. The instant you run into something the rules don't cover, you need to run it your way, and OD&D actively encourages this.

Ooh, here are two more ideas I have: a spellcaster who can equip like a thief in exchange for limiting his spell memorization abilities (only copies of one spell per level per day), and a mage who can cast spells at-will but they can only be evocation spells.

heh. My OSR unicorn have for a long time been having a OSR/TSR variant game that takes OD&D/Basic D&D and just converts all those 3,5/4e/Pathfinder classes, races, monsters etc, and reverse engineering it all backwards. The closest thing I have found is Blood&Treasure (with supplements). But my search of a true rosetta stone OSR neoclone yet continue... But I thinks 5e, being a kind of midway-point edition, killed of the prospect of such an endeavor.

Well, how hard could that be?  3.5, at least, seems pretty simple to convert. Classes are converted like I said, and monsters shouldn't be that much harder.  


Monster Conversion:

To get OD&D AC, start with d20 AC.  Halve anything after 20, so 22 becomes 21, 30 becomes 25, etc.  If you're using ascending AC, that's the number right there.  If you're using descending AC, subtract the result from 19 (or 20, whichever makes more sense for the edition you're using).

To get OD&D HP, cut the d20 HP in half (rounding up) and cap the results at 40 HP.  This assumes you're using d6 hit dice for monsters.  To bring the converted monsters in line with d8 hit dice monsters, divide the d20 HP by 1.6 instead of by 2 and the cap becomes 50 HP.

Monsters should only have a few special abilities.  Looking at Balor, a CR20 example from 3.5, we'd keep Spell Resistance 28, Entangle, Vorpal Sword, and Flaming Body, and discard all the rest.  

Higher-level monster attacks should get nerfed.  A CR 7 attack (chimera dragon's breath) goes from 3d8 to 3d6 (reducing average damage by 3), and the Balor's flaming body attack goes from 6d6 to 3d6 (reducing average damage by 10.5).  The pattern kind of looks like "reduce attack damage by CR/2" but it's a pattern of only two points, so I can't guarantee anything.

I think that's about all of it.  The number of attacks don't quite match up, but I don't think that really breaks the system.

Did I miss anything?

Quote from: Teodrik;1015811heh. My OSR unicorn

For a second I thought this was a class or something.

Quote from: Teodrik;1015811heh. My OSR unicorn have for a long time been having a OSR/TSR variant game that takes OD&D/Basic D&D and just converts all those 3,5/4e/Pathfinder classes, races, monsters etc, and reverse engineering it all backwards. The closest thing I have found is Blood&Treasure (with supplements). But my search of a true rosetta stone OSR neoclone yet continue... But I thinks 5e, being a kind of midway-point edition, killed of the prospect of such an endeavor.

This is true. It is far easier to run a 5e game than it is to reverse engineer classes to an older edition. You can even use the basic rules and ignore things like Feats and Backgrounds and just port over the content you want.