I can post the skill tree our group has been using for the last year or so if it'll help ya choose Vecna.
Posted from a different thread:
Monte's group uses a Knowledge (Monster) skill, though I haven't heard what system he uses. It was tossed around for a while for the PHB but was taken out for many good reasons.
The way we use it, it represents book knowledge or learned tales of monsters. Knowledge (Monster) being too broad and easy (who wouldn't try to put some ranks in it?), it was divided up. Very often no one will have any of these skills, but occasionally they come in handy. I had one wizard who specialized in studying various dangerous creatures and was diversified over all the fields. A successful check indicates knowledge of the base creature based upon your visual sighting of the creature or other clues (if the DM considers enough of them to be present). Any templates, advancement in HD, added class levels, or off shoots of the race are always unknown as they aren't in the books for every individual of every race. Of course on the brightside, this means you always roll against only the base CR of the creature.
Creatures your character has actually encountered and knows about first hand do not require checks (as the checks represent only book knowledge and hear-say).
We use CR because it allows the DM to keep back knowledge of the critter if he needs to, and because the difficulty of the check reflects the rarity of the creature (in general). And because it was simplest of course. Ack. Rambling on. Here's the system we use. Works great for us. Been using it for almost a year now.
Knowledge (arcana) - aberrations, constructs, dragons, ooze, shapechanger
Knowledge (history) - giants, humanoids, monstrous humanoids
Knowledge (nature) - animals, beasts, fey, magical beasts, plants, vermin
Knowledge (the planes) - elementals, outsiders
Knowledge (religion) - undead
Type of Knowledge.........DC
Common Knowledge........5+CR
Basic Knowledge............10+CR
Specific Knowledge........15+CR
Common Knowledge would usually include what the creature is, and what its usual reaction to people is.
Basic Knowledge would be a general physical description of a creature, its general level of intelligence, basic ecology, and general habitat.
Specific Knowledge would include strengths, weaknesses, and a detailed knowledge of about every trait of the most common example of the creature in question.
Ranks and successful knowledge checks in these skills represent information resulting from study, stories, and training. They do not include first hand experiences.
Also, in areas where creatures are more prevalent, specific traits of some creatures may be basic knowledge or even common knowledge. A border country constantly pushing back orcish hordes would know of the adverse affect of bright light on orcs. This trait would be common knowledge there. But to those in lands where orcs are a far off nuisance, only study would reveal this trait and it would be considered specific knowledge.
Side Note: We use Knowledge (Religion) for Undead as opposed to Knowledge (Undead) because a) Defenders of the Faith wasn't out yet and knowledge (undead) wasn't in print anywhere yet, b) because clerics have very few skill points to throw around, and c) because life and death, death and undeath are things we like clerics in our campaign to know about. It has worked out wonderfully so far. Especially against the Nightcrawler....
