nightveil specter?

[b walsh]

when nightveil spector exiles the top card of opponents library i can play it....do i have to pay for it or not???

[Gorzo]

Yes, you do have to pay for them. It would have to specify "without paying their mana cost" in order to play them for free.

The good news is that {Nightveil Specter} says you can play the cards, not cast - this means you can use lands of your opponent't that you've exiled to pick up those extra colors in costs that your deck doesn't have.