{Nightveil Specter} -- how many times may i play the exiled cards, and if its only once, where do they go afterwards?
Also, do i have to pay the cards mana costs?
You can play them once. It's just like they were in your hand and they go to the battlefield (creature/land for example), graveyard (instant/sorcery, for example), or wherever else they might go.
Gatherer's rulings:
1/24/2013 Playing a card exiled with Nightveil Specter follows all the normal rules for playing that card. You must pay its costs, and you must follow all timing restrictions, for example.
Hope this helps.
Do I get the "RESOLVED" stamp? :P
RESOLVED
YAY! :P :D
Ty vm!
No problem, always happy to help. :)