User blog comment:Commander Marko/Slender, Shadow of the Woods (Updated!)/@comment-5418658-20121104053911/@comment-4290320-20121104104757

After he casts an ability, there is a 0.5 second delay and he enters stealth (can't be seen by enemy champions, vision wards, minions and neutral monsters). When he loses stelath, his next autoattack will deal additional magic damage (his passive is similiar to Kha'Zix's passive, too).