So, a few more NPCs that have been brewing at the back of my mind...
Tanis Vassily, The Immortal Tiefling
So, there are a few rules most cutter should follow: never short-change a Devil, never question the Lady of Pain, and never, ever gamble with anyone involved with a Power of Trickery. Sadly, Tanis ignored that last one.
A Doomguard through and through, she believes in the Power of Entropy, and began explaining it presence to some random Gnomish Cleric in her local bubhouse, when she was already well in her cups. She claimed that Entropy touched everything - people, Planes, even Powers could and one day would die, rot, and dissipate themselves into nothingness. The Cleric begged to differ, and set her a challenge.
She had to die.
Simple as that? Tanis thought she'd be a fool not to take the Cleric up on such an offer, and settled a small wager. No-one's really sure what she offered, but she seems reluctant to tell anyone.
Needless to say, she packed up her things, sorted her last requests, and had a friend ready and waiting for a quick Resurrection spell when she won the bet. She came back to the bubhouse, found the Cleric, and stabbed herself in the throat. She was, understandably, very annoyed when she awoke in the local Healer's Rest, having been saved by a passing kindly Cleric of a Power of Healing. So, she walked back into the bubhouse, found the Gnome once more, and took him outside. She scaled the side of one of the many great buildings in the Hive Ward, and dived off head first - only to be saved by a passing laundry cart. She made several more attempts, ranging from starting fights with Fiends in the street to setting up complicated "certain death" traps, as built by her on-off accomplice Rikka Thornfoot, the Kobold Traps Expert.
Each time, she found herself alive and well - weapons were blunted, arrows missed, traps failed, circumstances led to her surviving even under the least likely odds.
She later found out that the Cleric was, in fact, a Proxy of some powerful trickster God of some Prime - and he had given her a "Gift" of luck. No matter the reasoning, she would always survive her attempts to die, forevermore, till she decided to give up and admit her defeat to the Gnome.
It's now many years later, and she is still searching for a way to break her "curse" - though every attempt has so far been met with failure. She's been using this luck to help with her previous career as an adventuring Thief - and so far, it's kept her out of too much trouble.
"Blessed" by the Power of Luck* 
Never Trust a Tiefling (3)
Surprisingly Chipper Doomguard (3)
*Note that this should only be used when she wishes to deliberately invoke it, or influence it in some way - she does not need to roll to avoid death. The Luck God's got that covered for her. It can be used, however, to figure out how injured, embarrased, or otherwise set back she gets without dying.
I nicked the idea from Hymneth over on Planewalker.com, which he posted up in their Adventure Hook Junction 1, wherein she was the focal point of the adventure - the players had to figure out how to kill her. I just thought I'd flesh her out, and stat her for Risus. I introduced her by having her crash through their roof, having spent the past 4 days plummeting through the Elemental Plane of Air, hoping to hit something, and eventually falling through a natural portal into Sigil, breaking her fall on steep rooftops, spouts, and finally the group's pile of cloaks and clothing.
In appearance, she's fairly short, just pushing 5 feet, with a wiry build. She has a grab-bag of Tiefling features - a reddish hue, three-inch horns, slightly pointed ears, solid black eyes and a few sharp teeth here and there. Her dark hair is normally wore in dreadlocks, tied back with a black ribbon.
Style-wise, she's all about the black - like and good Doomguard. However, she shuns some of the more sombre fashions favoured by the sect, and wears asymmetrical clothing, lots of jewellery and accessories, and a few stray piercings. She has the Doomguard symbol acid-etched on her left wrist, mostly hidden with bangles and charms.
Personality-wise, she's surprisingly cheery, cheeky,and fun-loving, for a cursed woman who thinks that eternal nothingness is the most fun thing she could be doing. She'll spend hours chatting about the finer points of Entropy, without slipping into the dour mood many Doomguard do.
She makes a great random NPC cohort, an adventure seed, or a general background character.