I don't know if my original posts about how to do this are clear enough, so here's a few walk-throughs.
I'm making a level 8 wizard as the main villain for an adventure. I have no strong theme for him that would suggest a series of linked mutations, so I'm going to corrupt him randomly. His spell list is as follows: Runic Alphabet, Mortal; Sleep; Color Spray; Patron Bond (King of Elfland), and therefore Invoke Patron (King of Elfland); Choking Cloud; Nythuul's Porcupine Coat; ESP; Breathe Life; Dispel Magic; Lokerimon's Orderly Assistance; and Control Ice. I roll an 86 on Table I, resulting in 22 failed rolls.
The first failed casting I roll up is Control Ice. At this point it's obvious that if you wanted more accurate detail you could develop the system so that the first few failures are 1st level spells, with the 4th level failures only coming in towards the end of the list, but this is good enough to suit me. At any rate, rolling on the results for a spell check of 1 for Control Ice, I get a 4, which is a misfire. Nothing of lasting interest.
Next, I roll up Sleep, and roll a 3 on Sleep's chart, resulting in another misfire.
Next is Patron Bond. This results in automatic patron taint, so rolling on that table I get a 3. This wizard becomes aloof and indifferent to mortal concerns. This is no big deal, so I'll let it ride. The wizard loses 1 Personality and I move on.
The next roll turns out to be a misfire, but after that a failed Color Spray leads to the caster having his skin changed to a rainbow pattern. That attracts a little too much attention, so I use one of my (8/2) 4 bonus Luck points to ignore that. The very next roll is a failed Lokerimon's Orderly Assistance, resulting in the caster becoming overly helpful to anyone who asks unless he passes a Will check. That makes for a very poor villain, so I use another bonus Luck point to nix that.
Twenty two failures is a lot to detail, but I go on in this manner, throwing out a good many of the failures because they were simple misfires, spending bonus Luck to eliminate a few particularly bad corruptions/taints, and having to deal with the rest. At the end of it all, this wizard has an aloof and indifferent manner (-1 Personality), horrid pustules on his face (-1 Personality), becomes withdrawn from mortal concerns (the same patron taint a second time, and another -1 Personality), shimmery sheen to his skin which has a green tone (two separate results), painful lesions and sores, flesh that flows and reforms on his legs, and a longing for Elfland. Now he's nicely weird, as a level 8 wizard should be.
Later, the characters are looking for a wizard in town to sell some weird magic reagents to, and he seems like he'll be a recurring NPC, so I stat him up quickly. Using the quicker method from part 2 of this series of posts, I roll a 78 for a level 5 wizard, giving this guy 5 failures. Since I'm using Table II, these are all corruption or patron taint, and I don't have to deal with misfires.
This guy's spell list is Charm Person, Magic Shield, Ekim's Mystical Mask, Flaming Hands, Ventriloquism, Shatter, Detect Invisible, and Write Magic.
The first failure is Ekim's Mystical Mask. I roll a 3 on the corruption table (this guy has no patron, so no patron taint), and find that he's taken to wearing hoods or masks in order to not reveal his true face.
The second failure is the same. No point worrying about it now...even if I had spent Luck on it before, he'd have to deal with it again.
Next is a failed Flaming Hands, resulting in a -2 on spell checks for any cold based magic. Since he has no cold based magic, this is nothing to worry about.
I still have two more failures to roll, and two bonus Luck points to spend, so I'm done.
Lastly, the PCs encounter a group of bandits with a wizard among the leadership. This is another 5th level guy, and I don't want to spend a lot of time on detailing him, so using the quickest method, I roll a 95, or 7 failures. I'm spending my two bonus Luck points to knock this right down to five failures.
First failure is 1 Minor, with a result of 7, chills. Next is 6 Greater with a result of 3, bull head. Next is Minor, painful lesions; Major, deep blue skin; and lastly Minor, hair falls out. Quick and dirty, but done in about a minute.