Intimidation keeps your hostages under control so a kidnap does not fall apart halfway through a restricted area. It needs level 2 and Kidnap.
Intimidation sits at position 10 of 19 in the Stealth tree. Unlocking Intimidation takes 2 skill points. You need level 2 and Kidnap before you can buy it. Jacob and Evie each have their own skill tree, so you buy Intimidation 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.