The official Pokémon movie blog has updated. Translations of the new entry follows:

Appear! Movie Details #8: The "Prison Bottle"'s Model Sheets Appear!



This the the "Prison Bottle", which was used to confine Hoopa (Unbound Form) when it went on a rampage 100 years ago. It's an important item that's very crucial to the story!


Source: http://www.pokemon-movie.jp/pokemovie_ch/?p=812