"[[Passive Ability]]: Stealth"
If this is Stealth as in under Cloak: No. Just no. Steal on a stick should not be untouchable by anything except mass CC. It is very strong and the forced combo isn't a hindrance when so many Darkness decks pack Nightfall/Eclipse.
The order doesn't really matter, I can still use a Nightfall, and then a Cloak to make the combo.
One question about the card:
If Nightfall gets destroyed, does this creature lose its ability?
And if the ability is lobotomized once, does it come back if another Nightfall comes in play?