That's planeswalking.
Blink works like this.
1) portal is ripped right where Xion is standing, making him rift into a "temp" plane.
2) portal is ripped where Xion wishes to go, from memory. Xion can only blink to places he can see. So if he's in a fog, blink does not work.
3) Xion rifts back to the plane from the "temp" plane.
Since this is all magic on the stack of time, it can be done in a second. Though there is a "cooldown" of this, since Xion needs to regain his balance and his bearings on where he is in the current plane.
So, thanks to this cooldown, Xion can not blink twice within two turns. Twice in three turns, yes. Blink-cooldown-Blink.
__________________
|