1 hp: add +2 to any d20 roll before rolling (up to 5 may be spent on any one roll)
1 hp: automatically stabilize
2 hp: maximize one damage die
3 hp: roll twice for hp when levelling, taking the best result
4 hp: get one bonus skill point
5 hp: re-roll any roll
5 hp: get one extra standard action
10 hp: force an NPC or other player to reroll
20 hp: get a bonus feat
30 hp: increase an ability score
