Click the character, then the button to select either skill. For hide in shadows, it is like casting a spell on yourself (ie ctrl right click on the character portrait). For Evil Eye it is like casting a spell on a hostile character - click on your targetted foe. Hide in shaows lasts for a good while and allows pretty good damage bonuses. Evil Eye is quite a bit tame when compared to a good ****STORM spell, or a good assassin dagger attack.
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Nordom, cousin to Davros