First Strike II makes your opening blow strong enough to finish some enemies before the fight starts. It is a six-point skill at level 6.
First Strike II sits at position 15 of 19 in the Stealth tree. Unlocking First Strike II takes 6 skill points. You need level 6 and First Strike I before you can buy it. Jacob and Evie each have their own skill tree, so you buy First Strike II 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.