You get an extra life every million points. Curses are given to you by wraith-like creatures and cause bad things to happen to you. Although if you stop and think about it, that double gravity curse should have another effect Levina the Sorceresses' uhh never mind. Gold keys are used to open up chests and are plentiful, while bronze and silver keys are used sparingly to open important areas. You can increase your level by collecting ten points worth of artifacts.
Bronze is worth one point, silver is worth five, gold is worth ten.
Well, not exactly. See, chests don't always contain treasure, they sometime contain curses or worse thieves. They're a balancing effect. You also lose all your weapons, armor, and scrolls when you die. This makes you choose your shots more carefully.