Hit points

[Jeraa]

Hit points can't really model what happens in books. The books tell a story - they don't follow game rules.

However, that 1st level character killing a level 10+ with a single crossbow bolt is possible, if you use the Vitality/Wounds system. Critical hits ignore vitality points and go straight to wounds. So that high level wizard (with say the normal 10 constitution), would have 10 wound points. At 0 wound points, you have to make a fortitude save or fall unconscious and begin dying. So, a 1d10 crossbow bolt can take out a wizard - if you use the Vitality/Wounds rules from Unearthed Arcana.

Edit: I also forgot - any time you take wound damage, you need to make a fortitude save or be stunned for 1d4 rounds. If you consider stunning to make the target helpless, you can coup de grace him.