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I'm pondering Hyperborea and The Lost City "reincarnated" from Goodman. Before I dive in and prep, I wondered if anyone else has tried such a thing? Things look straightforward, and I plan d20+FA+mods+AC 20+ for to-hit success--so clean. I might start with 4 core classes to keep things simple for players, but we'll see how "adventurous" they are.
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Most OSR type games/Modules/Settings are relatively easily transferred into and out of Hyperborea. Jeff purposely made the system compatible with a lot of systems, as they use all the same base system. Most of the OSE/BX/Castle & Crusades/and the others work with little conversion effort. The most effort is Monster/Spell conversions. The Combat systems are very similar, some may break things down slightly different, or have a different method for some part (Initiative, or Round sequence, Etc)...
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When I ran Goodman's "Into the borderlands" I used the AD&D 2e monstrous manual to fill in the gaps for monsters I did not choose to replace.
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What I like about the Goodman hefty book is the original is there, and there's the 5e version plus critters, so I am likely able to deal with the monsters, etc. (and I'v been GMing since '76, so on-the-fly stuff is doable).