New OSR GM questions regarding converting AC, and expanded random encounters?

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NewTruthNeomaxim
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New OSR GM questions regarding converting AC, and expanded random encounters?

Post Tue Oct 12, 2021 12:51 pm

I hope this is the right place to ask, but I am preparing to run Basic Fantasy throughout the winter, and have been slowly collecting resources. I was never around for OSR in its historic iterations, and my lack of experience has been showing up as I try to collect adventure sites, etc... from various game systems.

In short, some games use ascending ac, some descending, some both... Am I being daft, or is there a general equation or guidance for taking a monster from one ruleset to another, especially considering so many of these games beyond this one variation are essentially compatible?

Thanks so much!
Last edited by NewTruthNeomaxim on Tue Oct 12, 2021 2:29 pm, edited 1 time in total.
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Clever_Munkey
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Re: Any advice for a new OSR GM regarding converting AC?

Post Tue Oct 12, 2021 1:27 pm

The easiest way is to find that particular monster in the system you plan to use.

If that isn't possible, the monster's Hit Dice tell you just about everything you need to know: Attack bonus, saving throws, HP, experience, etc. can be found in the tables in the core rulebook all based on HD

As for AC, that depends a little. In BFRPG, unarmored AC is 11 so:

If unarmored AC is 9 descending, subtract AC from 20 to get BFRPG equivalent.

If unarmored AC is 10 descending, subtract AC from 21 to get BFRPG equivalent.

If unarmored AC is 10 descending, add 1 to the AC to get BFRPG equivalent.

If unarmored AC is 12 (only the case in one system I know of) subtract 1 from the AC to get BFRPG equivalent.

Alternatively, when in doubt pick a number that feels right for the situation.
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NewTruthNeomaxim
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Re: Any advice for a new OSR GM regarding converting AC?

Post Tue Oct 12, 2021 2:28 pm

That is fantastic, and super helpful. Thank you so much.

A follow-up question (so I don't clutter the forum with new threads), but if I add the field-manual monsters to my world's pool of possible options, are there any new tables for dungeon/wilderness encounters that account for those? Perhaps anything fans have written up?
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Dimirag
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Re: New OSR GM questions regarding converting AC, and expanded random encounters?

Post Tue Oct 12, 2021 3:20 pm

Check this, but is far from finished.

There is also this.
Sorry for any misspelling or writing error, I am not a native English speaker
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teaman
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Re: New OSR GM questions regarding converting AC, and expanded random encounters?

Post Tue Oct 12, 2021 6:10 pm

One thing in general, each point of AC is about 5%. So if you forget and subtract from 21 instead of 20 (or vice versa), it only makes a 5% difference. So if you're not sure, wing it and don't sweat things. The players never need to know the opponents AC.

And welcome to the OSR! For me, simpler is generally better (and I suspect that's true for many of us).
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NewTruthNeomaxim
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Re: New OSR GM questions regarding converting AC, and expanded random encounters?

Post Wed Oct 13, 2021 8:32 am

Thanks everyone, and thanks for the welcome.

I am excited about OSR as I recently realized the industry never left its ethos, but WotC sure did. I run a lot of Cypher System and its core tennet is "rulings not rules"... This sent me down a rabbit hole and I realized a lot of games follow this, and I simply no longer jive with those that are totally weighed down by math-hammer and specific rules, plus dice-rolling trumping players actually doing any mental work.

"I search."
"How?"
"Um... by rolling a search roll?"

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Solomoriah
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Re: Any advice for a new OSR GM regarding converting AC?

Post Mon Oct 25, 2021 8:34 am

Clever_Munkey wrote: Tue Oct 12, 2021 1:27 pm If unarmored AC is 10 descending, subtract AC from 21 to get BFRPG equivalent.
This bit is incorrect, actually. The games where AC 10 is unarmored (1E and 2E era) have leather armor with AC 7, chain mail with AC 5, and plate mail with AC 3, just the same as "basic" era games do. The only difference is the unarmored AC of 10. So, for ALL games with descending AC, subtract from 20, and if AC is 10, make it 11.
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Solomoriah
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Re: New OSR GM questions regarding converting AC, and expanded random encounters?

Post Mon Oct 25, 2021 8:36 am

NTN: Instead of saying "How?" you might try saying "Describe for me how you are searching."

With a good enough description, many items may be found without a roll at all.
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rudgar
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Re: New OSR GM questions regarding converting AC, and expanded random encounters?

Post Thu Oct 28, 2021 1:11 am

20 minus descending ac is the correct answer (as Solomoriah said)
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