Knife Master I gives throwing knives a stun and refills them when you land Multi-Kills. It opens at level 3 for both twins.
Knife Master I sits at position 17 of 19 in the Stealth tree. Unlocking Knife Master I takes 2 skill points. You need level 3 before you can buy it. Jacob and Evie each have their own skill tree, so you buy Knife Master I once for each twin.
Air Assassination
Drop onto a target from above and kill him in a high-profile strike.
Assassin Steps
Greatly reduces fall damage, silences your landings and makes your movement much quieter.
Chameleon
In Sneak Mode, Evie becomes invisible while standing still; only enemies very close by can spot her.
Double Assassination
Kill two nearby unaware enemies at the same time.