Dishonored - Runes & Bone Charms
I have now collected quite a few runes & have unlocked Dark Vision stage 2, Vitality, Agility & Shadow Kill which turns unaware foes to ash (this is useful because it means I do not need to hide bodies).
Another collectible in the game are Bone Charms these grant you an effect when activated. I have quite a few of these like River Affinity which increases my swimming speed.
I have not played the Thief games by (Looking Glass/Eidos) but I imagine that Dishonored borrows quite a bit from that series? I have not said much about the storyline, you are Corvo a bodyguard to the Empress & after she is attacked & killed you are sent to prison. You then obviously escape the prison & set out to avenge the death of the Empress whilst also finding her daughter.