Slowcake’s Exceptionals is conducting a poll: in the eyes of Londoners, what variety is their soul? Do you have a plain, unadorned soul? Brilliant, maybe? Not discordant, as those do not exist. Or for the greatest among us, even coruscating! Seekers need not apply.
For example, I would say my character has a brilliant soul, as they are pretty mid-game, POSI and all that jazz, but certainly not anywhere near something that would elevate their soul to another level.
Back in the day I wrote a whole roleplay cycle about my main char’s quest to upgrade her soul to Coruscating…
She’s now working on whatever the next stage is 
Serious answer: Stained a deep, choking black, like the plumes of smoke that ooze out of Mr Fire’s factories – but shot through with brilliant light, like the electricity that crackles within a storm-cloud.
Silly answer: Queer.
Pretty average soul, since they sold it early (barely out of prison), and they just recovered it a few weeks ago. I don’t think 8 years in a glass prison makes any soul brilliant or coruscating.
No one has seen Stanley’s soul in ages, but the last viewer was rumoured to have screamed piercingly for 10 days straight, until her family finally gave up and shipped her off to the North. Last heard, she’s still shrieking on the shores of Codex.
I’m not sure, but at this point in the game (very late-game stats above the previous limit), I’m guessing some very high (or at least high quality) quality (as devils seem to pay more for POSI). Albeit upgrades in stats, notability, or POSI2 or more, doesn’t seem to matter when it comes to what devils are willing to offer for your soul. Not that I would sell my PCs soul to that swine. But I don’t have Paramount Presence because it’s quite expensive and there’s not really any gain from it (at least not that I know of).