Two Against Darkness - The Method

03 Feb, 2025

This is a new way to play your B/X compatible adventures. Anything where the monsters are measured in Hit Dice really. With a single index card you can convert adventures into romps for two Dungeons & Dragons 4th edition characters.

I know, right? But this actually works. And after trying (and loving) it, it ends up blending the emergent gameplay of the OSR with D&D4's tactical power fantasy to create something familiar but wholly new. It's quick and snappy unlike D&D4. It preserves that OSR adventure quality and problem solving. But the characters are crazy powerful and have fun superhero moves. But danger is still real somehow?

In this post I’ll cover the method. In the next post I'll cover the rationale behind it and how to extend it to higher levels.

The Vision

It'd be foolish to just convert B/X adventures to D&D4 one-to-one. The game would slog and if I'm playing with a full party why not just play B/X? I want to run a bunch of old school adventures I've collected. I have access to maybe two players most of the time. I don't love hirelings and I do love D&D4. Let's bring out the strengths of both and make something new!

So my goals are:

• Be playable with just a cheat sheet and the module, no combing over statblocks ahead of time.
• Designed for 2 players or 1 player and a companion character.
• Preserve the overpowered heroes feeling of D&D4 characters.
• Complement with the looser rulings play of B/X.

In other words, you should have the social and environmental play of the OSR but the characters themselves are like 4 times stronger than a normal character.

Wait, I Don't Know D&D4!

You can download H1: Keep on the Shadowfell for free on drivethrurpg here. It has quick start rules to learn the game and five pregens you can use to play this with. If you get into it, the Player's Handbook is super cheap second hand and the Rules Compendium is all you'll ever need from a rules reference.

The only change I'd recommend making out of the box is use some kind of side initiative (I like speed sandwich with an initiative DC equal to the medium DC). Just let everyone take their actions at once. Friends don't let friends use individual initiative.

The Method

All monsters are converted into D&D4 minions, mobs, monsters, elites, or solos based on their HD relative to the heroes. 1st level D&D4 heroes are 4HD, so monsters of about a quarter of that HD become minions, monsters of about a half become mobs, monsters about the same become monsters, monsters about double become elites, and monsters about triple become solos. I'll use the example monster Angelica the Ursaloth from The Merry Mushmen's Raiding the Obsidian Keep. It's a good example of a harder monster to convert to show you it isn't bad.

Angelica the Ursaloth-An amphibious enchantress with octopus tentacles for legs AC 3[16], HD 2 (9hp), Att 3x tentacle (1d4) or unwanted kiss, THACO 18[+1], MV 60' (20'), SV D12 W13 P14 B15 S16, ML 8, AL Neutral, XP 30 -Unwanted Kisses: +4 to hit an unwary or surprised target. Her lips are toxic, save vs poison or die in d6 turns. -Seductive Song: Her voice is sultry, save vs spells or be charmed to protect and obey her. Killing her breaks the charm. -Hungry Friends: She summons two harbor sharks to defend her.

Your index card gives you the stats you need. Only HP and damage are affected by type, you’ll use the same attack bonus and defenses regardless. If you feel like it's worth an adjustment, you can add +2 to a defense or to attacks.

Most of the information in the stat block can be ignored. We know her attack bonus is +6 vs AC for her tentacles and +4 for her weirder attacks. She's HD 2, so that means she's a mob and has 16hp. She seems willful so let's give her a +2 to Will for AC 15, Fortitude 13, Reflex 13, Will 15. She attacks three times with her tentacles and has 2d6 to work with, so let's just give her two attacks dealing 1d6 each time. At the table when she's encountered, I'd just look at the card, write down her name, her 16 hp, and her Will 15.

Largely follow the special abilities as the OSE stat block. Abilities that provoke a saving throw become attacks against an appropriate defense. For saves against truly monstrous effects like permanent domination, petrification, or instant death, impose damage or a lesser version of the effect on hit (save ends) then impose the full condition if they fail one or two saves. Liberally interpret OSE spells into D&D4. You don’t have to be perfect or even consistent with D&D4.

Angelica's Unwanted Kiss kills in 1d6 turns on a failed death save. We can basically do the same thing here, we'll make it an attack vs Reflex to impose ongoing 5 poison damage (save ends), and on the first failed save you'll die in 1d6 turns. Her Seductive Song is similar, it seems like she can do that as much as she likes on her turn. Let's say as a minor action she makes an attack vs Will against everyone that can hear her. On a hit, you're dazed (save ends). First failed save: you're dominated (save ends). Second failed save: you're dominated until she dies or the curse is broken. Hungry Friends just means we'll also fight her with some harbor sharks, that's easy.

This means when they encounter a new monster, all you'll have to do is write down the name, HP, and their good defense. Everything else is already on the index card. When a special ability comes up, just figure out what defense its attacking and if you need to delay the effect.

Against Boring Encounters

When you enter an encounter, draw a shitty map of the area as it is. If there's nothing going on, add something to interact with. Cover, pits, a trap, fire, high ground, difficult terrain, furniture, treasure, a third-party.

If it’s an encounter against all the same type of enemy without many special abilities, choose a template based on personality:

• Wolf Pack: All enemies can shift 2 1/turn.
• Double Line: 1/2 get ranged attacks, 1/2 get +2 AC and mark any targets they hit or miss for one turn.
• Commander and Troops: Choose one to be the leader. Upgrade it from minion to mob, mob to monster, etc. Gives allies within 2 of it +2 to attacks.

If they encounter 3d6 skeletons that'd be a pretty boring fight. If they do fight, let's assign them Double Line, giving half of them javelins and half of them scimitars and shields.

Basically, you're adding monster roles (skirmisher, artillery, soldier, leader) to spice things up. The other roles (lurker, controller) depend a lot more on special abilities, you'll know them when you see them. Brutes don't really factor in here.

Magic Items and Traps

If a consumable item or trap does damage, double the damage dice. If it heals, it'll let them spend a healing surge.

D&D4 expects magic weapons and implements (staves, wands, holy symbols, etc.) to give an enhancement bonus to attack and damage rolls using them and bonus dice to critical hits equal to that bonus. So for our purposes, magic weapons and implements they find should give a +1 enhancement bonus and deal +1d6 damage on a crit. For the most part, use the special abilities of magic weapons and implements as is. If they find a +2 weapon, that's a +2 enhancement bonus and it'll deal +2d6 damage on a crit. Lucky them!

Here's example of an item conversion again from Raiding the Obisidan Keep:

The bearer of the Holy Staff of Vitela takes half damage from Chaotic magic and can touch the staff to a Chaotic creature to banish it from this plane of existence once per day. While D&D4 would never print something like this, this is fine actually! Don't dampen the energy of B/X adventures just for adherence to D&D4. In fact, this is a magic staff so it should give a +1 enhancement bonus to implement attack and damage rolls made using it and should add +1d6 damage on crits using it. I'd even let clerics use it as a holy symbol, even though its a staff. It's holy after all!

Improvising

On the top of the card are three DCs. The Easy DC is 8, the Moderate DC is 12, and the Hard DC is 19. Whenever they do something risky or need to avoid a consequence, ask them to make a skill check against one of the DCs. They can tell you what skill they're using. Default to Hard and talk yourself down based on the circumstances. Don't roll too often! Most actions can be resolved through simple description.

Experience Points & Gold

There's a simple way to handle experience points and leveling up: just make all D&D4 characters level up with the B/X Elf's XP progression. Then count XP exactly as you would in B/X! We use the Elf because all D&D4 characters are both fighters and magic-users in their own way. If you use an impromptu skill challenge, just give them XP as you would in D&D4. Gold is fine as is, but if they want to buy magic items only sell common ones at double price.

Making Your Notecard

If you can read my handwriting you can print mine out. Otherwise, here's how I made mine.

The first five lines are non-negotiable. These are the basic numbers you'll need to reference all the time.

Beyond that, it's up to you what you put on the notecard. When I ran this for the first time, my notecard looked like this:

I've got reminders for Reaction rolls since I tend to forget what the bands are and I've got little tidbits of the procedure: terrain, encounter types, and help ruling weird abilities. At the table however, I really would've preferred just some blank space on it to keep track of HP. Since that's what it's for anyway! The card really is a cheat sheet, and the rest of it is just for you to remember anything you'd forget easily.

Play!

That's all there is to it! If you give it a shot please let me know (or alternately if you want to try it let me know). It's untested and I'd really like to put it through its paces.

I'll talk about the rationale and extending it to higher levels in part 2.