Amplify Destruction will occasionally strike another target thereafter.
(Active 3) Unseal
He will not cast multiple Unseal stacks after each skill reset. Instead he will choose to keep attacking until his Unseal duration wears off, he casted Celestial Punishment or after no more enemies can be attacked, whichever comes first.
(Passive 1) The Hidden Truth
The Hidden Truth can detect vanished enemies. "[...]steals 33% of damage" is supposed to mean Lifesteal.