"He was the first to sacrifice his body to gain immortality as a lich. He used his magic to raise up an army of undead and conquer an empire. He was betrayed, dismembered, and swallowed up by the Shadowfell to fight a war against his one-time companion and eternal rival for eons. And eventually, he stole divine power for himself to complete his apotheosis and become the god of secrets, the undead, and necromancy."
(An amazingly concide summary of many edition's worth of Vecna-canon if I do say so! It smoothly fills the current Shadowfell in for Ravenloft but otherwise manages to include nearly everything one needs to know about this deity.)
"Yet for all that Vecna embodies the darkness, he is also the god of secrets, the lord of whispers, and the keeper of forbidden knowledge. Given the wickedness at large in the world, almost anyone would agree that some things should remain hidden—that certain truths should be left undiscovered. It is in this capacity that some unlikely individuals find their paths intersecting with those of light’s champions to keep secret what should never be revealed."
(The article is mainly on how to play a devotee of Vecna so here we have a perfectly justifiable reason to play an evil character among your standard party archetypes. It has an almost X-Filesy angle to it, albeit not Mulder and Scully searching for the truth but rather, your Vecnan is the shadowy Cigarette Smoking Man instead.)
"Vecna was once a mortal of great magical power. Magical mastery enabled Vecna to secure temporal power, with the assistance of his companion Kas. At some point during his ascent, he created the Lich Transformation ritual, then became a lich, and finally authored the Book of Vile Darkness...."
"...there are tales about how Vecna was born to a despicable witch who showed him the path to darkness before she was herself cast into a pyre by righteous zealots."
(Here is a couple more snippets showing the background of Vecna. I am not sure if he was attributed to the Book of Vile Darkness before, but it seems to work with the direction of the article. More on that in a bit. The bit about his mother being a witch and pyred is slyly from the Vecna: Hand of the Revenant graphic novel. Not canonical but full of tasty story elements that have been picked up by later authors over the years. Here again, it works with the point of Schwalb's article.)
"Too many variations exist for anyone to discover the actual truth and this is just how the Maimed One wants it. Keeping the circumstances about his rise to power secret ensures no one can replicate them."
(This is a briliant suggestion for using all references about Vecna, no matter how lame or contradictory. Even placing his reign in a timeline is difficult because everything about the God of Secrets is a myth at this point, and thus no one can know for sure but him! And maybe Kas...)
The article continues on with the Whispered Commandments, common to all cults of Vecna no matter how fractured they may be; 1. Follow the Subtle Path, 2. Nuture the Seed of Darkness, 3. Reject All Deities But Vecna. I won't go into the details but it's good stuff.
Next up is a section on the Keepers of the Forbidden Lore, a special sect of Vecna, useful for a PC follower:
"Contemporaries of Vecna when he walked the world as a lich, they were enforcers charged with gathering dangerous lore and returning it to him, whereupon he studied and perhaps compiled it in the Book of Vile Darkness."
(These people do not want the world destroyed as a Tharizdunite would, or overran by undead as a Kyussian might. No, they want to save the world like any other hero. Except that they find and lock away any dangerous knowledge they find until which time their master wants to make use of it.)
The rest of the article is on more motivations for playing a Vecnan, choosing suitable races, classes and so forth. It finishes up with some deity-specific Feats for a follower of Vecna. For obvious reasons I won't cover those here, but needless to say if you play 4th edition they should be what you need for your next evil character. I may give it a try myself someday.