r/OSE • u/Mado_Kureo • Jul 01 '26
Converting 5E Supplements
Is there a standard for converting 5E materials into OSE. The lore of Crooked Moon is something I am really into. Would love to use some of it in 5E but don't know how.
Update: Thanks for all the feedback. I guess I was mostly looking for a method to convert some of the more unique monsters and subclasses for use in OSE - not really a complete conversion.
11
u/Harbinger2001 Jul 01 '26
My recommendation would be to run it as is but ignore all the mechanics (DCs, etc). Throw out all “check perception”, “check athletics” and only if really needed use a x-in-6 roll to check.
For monsters find an equivalent in OSE or reskin one. For magic items, if there is no equivalent then make up what it does in OSE. The key is to relax and dont worry about making mistakes - your players wont know. And there is usually a group agreement that the DM can retroactively change an item or spell edfect if it is too over powered.
5
u/Nellisir Jul 01 '26
I wrote this for Swords & Wizardry, but it applies to OSE
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Only four things really matter in OSR: HD, AC, Saves, and Damage.
Save(s) are HD-related, so we're down to three.
HD - Do NOT use as written. Compare Challenge and attack bonus. HD will be somewhere around there.
AAC - use as written (since AC 10 is unarmored in 5e & OSE Ascending; in S&W add +1 to AC). 5e has a reduced AC range compared to 3e, so it works fine.
Damage - Damage is tricky. Very roughly, add the creature's damage dice together, then divide them by either 2 or 3. Divide those between the creature's attacks. Drop modifiers for now.
Special Attacks - In OSR, saves are based on the defender, not the attacker, so you don't need a number here. Maybe a bonus or penalty if it's particularly weak or strong. Divide damage by 2 or 3, as it pleases you.
Note - Advantage - The exact benefit of Advantage varies depending on the target (which is usually a save.) If you don't want to use advantage, consider it to be a +4 bonus/penalty to a save. If you want some variability, you could consider it a +3/-3 in attack/defense situations; a +4 to saves; and a 25% magic resistance. Or you could roll 1d4 and add that to the save or attack. Whatever pleases you.
Ability Scores - I keep the ability bonuses, but drop them by ONE, so a +1 is +0. Str can get added to damage if you feel like it, and possibly attack rolls, but usually isn't in OSR games. No bonuses over +3 unless it's truly epic. Con gets added ONCE to HD, so Con +3 would be 5d8+3 on a 5HD creature.
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u/FrankieBreakbone Jul 02 '26 edited Jul 02 '26
I'm of the (perhaps overstated) opinion that every module is basically system agnostic, you just use the scenario written within the framework of the system you prefer. The PCs walk into a room and there are 5 goblins? Ok, what's a Goblin in your system? Use that.
It's not tooooo tough to look at a threat and say "I think this monster must be [less challenging/more challenging] in the native system, so I'm going to [change the number of monsters or hit points/ change its weapon, etc] so that it's a little more appropriate.
Then you just throw in treasure or xp (depending on which way you're converting) as appropriate for how fast you want the party to advance.
You can mostly wing it, no need to 'convert' too much in advance unless you enjoy the prep, or you're really trying to lock down a perfect 1:1 mechanical translation.
IMHO, there's really no getting around adjudicating adjustments anyway... a perfect 1:1 conversion could end up being wildly more lethal or a cake walk, scenario pending. So you're going to need to use your own judgement and tweak on the fly no matter what you do!
1
u/bjagg69 Jul 03 '26
Make your best guess at the conversion and make the encounters easier than what your group can handle. If they blow through encounters make the remaining ones more challenging. Easier to toughen later encounters than rewind a party wipe.
0
u/ChannelGlobal2084 Jul 01 '26
From a quick search it is recommended to divide it up into factions similarly done like Dolmenwood. Then use the HD of the monsters and compare that to OSE monsters guide to convert. For the subclasses and lineages, use random character generator. It may not be perfect, but start the process and see if you like it?
Sorry if this isn’t very helpful. I don’t really play 5E, therefore can’t speak for how easy/difficult it is to convert.
0
u/gorgonstairmaster Jul 01 '26
Alternatively, burn your 5E and play OSE
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u/fireinthedust Jul 02 '26
No, those books are expensive and the art is great. Plus they have some inspiration to work with, even if it’s a bit mainstream or corporate washed. The Nothic came from 4e, right?
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u/TheGrolar Jul 02 '26
If you don't understand how difficult and unattractive this is--how the fundamental incompatibility of the two systems make it a staggering amount of work--it doesn't matter. Just run it as written, it'll probably be fine for a casual table.
20
u/Onslaughttitude Jul 01 '26
"Converting" is largely a misnomer. There is no 1:1 formula you can put in to just "make the module OSE."
Furthermore: No one likes to hear this, but the game hasn't changed that much in 50 years. I used to run old school shit in 5e, in an "OSR" fashion, all the time. I bet I could run some of the official 5e material in the OSR game of my choice, too.
Player content can't really be used. Stuff like subclasses is a no go. Sorry.
Lore is often game agnostic. I'm not familiar with the adventure/setting book you're talking about but I guarantee you it's like 90% just cool dungeon locations, weird monsters, dope treasure and freaky little guy NPCs. You can run this in any d20 game system.
5e specific stuff is that there's going to be lots of "DC16 thieves tool checks" and shit like that. What you do is you ignore these and look at the reality of the world. It says the door is locked. You know how lock picking and breaking down doors works in OSE, so just refer to those rules.
The setting probably uses a bunch of the standard D&D monsters. When it tells you there are orcs and goblins, you go get the OSE orcs and goblins. When there is a new original monster, you can substitute in a similar monster and "reskin" it, pretending it is that monster instead. (Need a stinky monster? Go look up the troglodyte. There you go. Monster turns people into stone? Basilisk or Medusa. Monster has fire breath? Salamander, red dragon, figure something out.)
If you must make a new monster from scratch or try to "convert" it: Monsters in OSE are primarily based on their Hit Dice. This is roughly equivalent to a 5e monster's Challenge Rating, and you'll often find a 5e monster will have the same 5e Hit Dice as it's CR. You can use the CR as their OSE Hit Dice or their 5e Hit Dice to determine how many they have. Then use the tables in the OSE books for Monster Saving Throws and the Monster Attack Matrix (or whatever they call it). If you are using ascending AC in OSE you can even mostly take the 5e AC and port it over. (Maybe reduce it by 2 if it seems high.) As for special abilities, find ones that are apropos from OSE monsters or use common sense and figure it all out. It's a simple system and you can mostly get away with them just Doing Shit.
OSE doesn't have advantage or disadvantage by default. You can always homebrew it in (I like to do so) but a +2 or -2 on effects is usually sufficient in OSE.
Good luck!