If we had an otherwise typical D&D world in which magic is the domain of magical creatures and particularly outsiders, and the only way for mortals to gain magic powers is through warlock pacts, what would the consequences of that be? What implications could that have for society, and how would it impact parties of PCs?
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While I enjoy 5E, the very high magic level assumed in all settings does grind my gears. I prefer my settings to be more Hyboria than Middle-Earth*, and this change would do a lot to support that. Personally, I would want to couple it with a tightly restricted race list. It would be either humans-only, or humans and "human-plus" races (tieflings, half-elves, hexbloods, et cetera).
One effect on society would be that any time you see a spellcaster, you know that person has a Boss somewhere, and the question of who that Boss is becomes of paramount importance. Each society would have a list of patrons they were okay with, and patrons that were extremely
not okay. Also, the warlock spell list is very short on spells that let you create permanent or long-lasting area effects. So you wouldn't see much of that.
From a player perspective, I think you would see warlocks being stretched to cover the roles normally given to other types of casters. The "arcane blaster" role would go to the patrons that grant access to
fireball (the Fiend, the Genie). The "healer" role would go to Celestial warlocks. Tomelocks would be favorites for utility spells. Also, play would shift to emphasize the short rest over the long rest, since all of the classes that rely heavily on daily resources have been whacked.
...You know, I may pitch this to the players for the next campaign I run. Most of them favor martial PCs, and they overwhelmingly prefer humans to any other race, so it would be a good fit. There are only two dedicated "caster players" in the group, and one of them is me, so I just need to make sure the other guy is okay with it.
*Actually, even Middle-Earth is considerably lower-magic than D&D.