Diabolists (Debauchery, Incantation, Consumption, and Diablerie)
Summoners (The four Goetic Arts)
Other (possible combination of Maleficia and Goetic)
I have recently had the opportunity to read "Realms of Power: The Infernal". A number of different points regarding it caught my attention, but there's one aspect reflecting back on the history of the game which I thought I'd bring up.
Several of the Maleficia (Debauchery's bloodletting, Incantation, Consumption, and Diablerie) and the Goetic Arts resonate very strongly with the practices of the Colossi of Dis described in the 2nd Ed. sourcebook "South of the Sun". Inhabiting what can only be assumed to be a giant, multi-leveled Regio accessed by crossing the "Line of Fire" near the Equator, the Colossi are masters of an advanced civilisation representing the single most successful tradition of Infernalism anywhere in the world. As Masters of Demons, they have largely bent Demons to serve their will, while experiencing an inevitable degree of corruption as a result.
I'm curious as to whether those of you who are familiar with the Colossi feel that they should be considered a Diabolic Tradition with the four Maleficia mentioned above (Debauchery, Incantation, Consumption, and Diablerie) or whether they pursue the four Goetic Arts instead. Furthermore, would you classify them as a Corrupted Tradition, Misguided Tradition, or something else?
Well, the Colossi get all of their power from dominating others and stealing it from them.... the most important example being Loshandar. So I'd say that they are a mixture of Maleficia and Goetia. They don't summon things unless you count Loshandar. And I don't really see them committing ritual acts of evil such as you see in diabolism (other than sacrificing to Loshandar, that is).
They are definitely a misguided tradition, because they don't think they are infernalists. They think they are good guys using the power of evil against itself.
Coincidentally I was looking through the PDF of South of the Sun around the time I picked up RoP:tI because I was looking at how hedge traditions might work.
It struck me that the Colossi powers depicted in SotS nearly all fall under the Goetic Art of Ablation (Cull the Life, Cull the Virtue, Cull the Spirit etc) and Summoning (The Call) rather than the Maleficia but I'd have to check.
IIRC they had a possession ability and could use their powers on creatures other than spirits (animals, humans etc) - how you model this gets a bit trickier.
I suspect they are a Misguided Tradition - they are similar to the followers of the Peacock Angel, the Mulhudin, but seem to be deceived they are in control. I don't think they would need to have any Hermetic abilities at all.
The Colossi's powers, adapted to be updated for 5th Ed., most strongly resemble the Goetic Arts. In fact, they are somewhat stronger than most Summoners in the application of their Arts because they can affect corporeal, mortal beings as well as those of pure spirit. Given that Nicolai the Spirit-Master from "Hedge Magic" was updated to be a Summoner, and he regularly used his Summoning to call animals and people, the parallel is established.
Perhaps the Colossi of Dis tradition should qualify as its own new Major Virtue. Those trained in it can use their Arts to affect corporeal and mortal beings as well as spirits. Ablation can be used on mortals, but each application costs some permanent loss, at a minimum of the trait Ablated, but likely a permanent body level as well.