Back in the day, I was running a game with friends. They both decided to play precocious kids, with a lot of power (magical and family) but in need of extra guidance.
So, they had a DMPC that was from Maine, and had the stereotypical accent like Fred Gwynne had in Pet Sematary. So he's talking about systems of magic, gods and spirits in that Mainer drawl.
We ended up playing pretty much every night for a month or two, and with me doing the accent so much, I had trouble shaking the accent irl.
It was a great fucking campaign tbh. We had a shit ton of fun just rampaging around and wrecking shit with their pair of grossly wealthy and grossly over powered siblings and their "uncle". The two kids were British, so those cheesy accents were in play, and they were from a posh witch family, which makes this post extra funny for me.
FAK MEY LAYBUR AYNT LETTIN MEY TACH THE FAKKIN DEAD. BANCHA FAKKIN POOSEES AAR GAVMINT. DANT NAA VA FEERST FING BAUWT RAYZIN ZOMBEYS VAY DOUW. EETS SAYF, AND YER SAUWL AYNT GONNA BEY DAMMED. OI JAS WON A FAKKIN ZOMBEY ARMI, AND THEM FAKKAS OVER IN CAANB'RA WONNA SPEET ON THAT.
YEER, MAYT. CORZ YA KAN YOOZ VEY AS A NEEKROMANTEEK KATTALEEST, REVOIVS MEY WONS OI GEET OWTA BEED, WORKS FER THA SKELLIES, TU. EET'S LOIK THEY SEL POWSHUNS AT THA SERVOW, NEED'TA TOLK TA SEVENELEVIN BOWT GETTIN' MOI BREW STOCKED, PERFECTLY NATURAL, EETS ALL FEIR DEEKUM STRAYAN, BEETA YEWKALEEPTOOS AN BANKSEEA, VAT AWL.
Maybe I've just played too much Shadowrun with too many Australians, but lots of them ended up speaking like that, even when they weren't meant to be Australian! :)
Most of the posh sounding characters are posh, or at least formally educated. Gale is a wizard (clear enunciation for spellcasting), Astarion ws a magistrate, Wyll is the son of a duke, Minthara is a princess.
Karlac and Halsin aren't posh and don't sound posh.
I'm not sure about Lae'zel, but that just leaves Shadowheart. Maybe Shar has a thing for accents?