[maximara]

Originally Posted by Opellulo

Just my 2 cents:
1. "Custom" settings can be a real pain for your players, they don't know how they work, what their characters can (and can't do) what to expect and what to aim for. I think this is the main obstacle of many campaigns, for this reason i always go with "known" worlds and then i adjust on the fly. Personal experience form my current witcher campaign: it's already a 3 in 1 setting (books, video-games and TV show are WAY different) but in this way the players have a baseline to anchor... Nevertheless a player asked me "how to became a paladin" that don't exist in any version.

This seems to be self contradictory as about any setting can be "custom" even the ones that are insanely flashed out. For example, I would hazard that more people know the lore of Azoroth than know that of Grayhawk or the Forgotten Realms. Heck, back in the early the early days we had a joke: "Forgotten Realms? Yes they are exactly that...forgotten."

Even settings that are fleshed out in GURPS be it Infinite Worlds, Merlin-1, Yrth, Star Patrol, or Roma Arcana will have details that players are unfamiliar with.

For example, Prime Directive is a variant of Star Trek (Star Fleet battles) that everyone thinks they know...until you get to the details and you realize this setting is "alien" and even the "canon" is a mess.

Even Five Earths with its variant of our Earth (Infopunk Earth) and a 4th century D&D-like world with King Arthur (Fantasy Earth) has a lot of unanswered questions.