Quoted By:
? = Hoopa will be a roaming Legendary in its normal form, opening hyperspace holes all across the region and hiding within one. Each hole can contain nearly any Pokemon that does not normally appear in this region (except Legendaries.) When you find Hoopa, you can potentially capture it, but if it gets away a random Legendary NOT native to this region will encounter you from that hole and Hoopa will open new ones.
If this occurs a set number of times, Hoopa will appear at a final, special location in its Unbound form. This is your only chance to capture Hoopa Unbound, but if you fail a final, random mythical Pokemon will encounter you from the final hole in Hoopa's place and Hoopa will disappear forever.