A Devil path sounds even more appealing that the already heavily advertised Lich one.
So anyhow, for the Pathfinder lorefags out there, how does one turn into a Devil and where would one presumably fit within the Infernal Hierarchy?
Traditionally, the way is pretty rigid, as befitting of the Nine Hells.
First step is to ensure you take actions during your life that will have your soul end up there. The easiest is to just sell your soul to a Devil, but there's a risk your soul will end up consumed instead. You have to be careful wording the contract, but you don't deserve to be a Devil otherwise. Alternatively, you have to be LE and live your life to the full according to your alignment, not be a pious follower of a god that will take you to his realm, and not be an atheist (Pharasma will lock you up in her vault if you are). Devoutly worshiping Asmodeus is probably your best bet, but not the only one.
Second step is the easiest by far. You just have to die and not be resurrected.
Third step is where it gets unpleasant. If you did step 1 right, you'll end up in Hell as a petitioner. You'll then spend ages getting tortured until you either break or become cleansed of any lingering mortal frailties like empathy and such. If you break from the torture, your soul will get used for something or other and you will cease to exist entirely. If you don't break, you will eventually be turned into a Lemure, the lowest of Devils. Congratulations!
Fourth step is to advance in the hierarchy and get turned into progressively stronger forms (an advancement always involving torture and excruciating pain), but that's beyond the scope of this guide. Just use your wits.
Mythic Devil will, fortunately, almost certainly skip the usual method. I wouldn't be surprised if the epilogue has you installed as a Duke of Hell after delivering a crushing victory against the hated Demons and probably instating the second devil-worshiping nation in Golarion.