Text (FS+errata): When a nonblack creature enters the battlefield, sacrifice ~this~. If you do, destroy that creature. [Oracle 2009/07/08]
The sacrifice is not optional. [Future Sight FAQ 2007/05/01]
If more than one nonblack creature comes into play, this card will trigger for each of them. The first trigger that resolves will have you sacrifice this card and destroy that creature. The other triggers that resolve will be unable to sacrifice this card so they will not destroy any creature. [Future Sight FAQ 2007/05/01]
You choose the order the triggers go on the stack if they all happen at once so you can control which creature will be destroyed. [D'Angelo 2007/06/04]
