"Until your next turn" means the effect wears off as soon as your next turn starts, even before you untap. It's basically the same as "until the end of the turn of the player who immediately precedes you."
01-02-2006
wotc
The card is cast using all normal rules and restrictions for casting spells. Casting it means you'll have to pay its mana cost, and it will go to the graveyard after it resolves or is countered. The only thing that's different is you're casting it from the Exile zone.
01-02-2006
wotc
If you don't cast the card, it stays exiled.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.