If a creature regenerates or has indestructible, it won't be counted when determining the value of X.
01-06-2011
wotc
Any triggered abilities that trigger because a creature was destroyed won't be put onto the stack until after Phyrexian Rebirth finishes resolving. This means the Horror creature token can be targeted by those abilities, if applicable.
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.