A dimensional Hole is a passageway from the future to the past(or visa-versa) that appears in the Pokemon:Mystery Dungeon series. It first appears when Dusknoir is taking Grovyle back to the future. Another one appears in the Hidden Land when Dusknoir once again attempts to bring Grovyle back to the future. It is highly suggested that dialga opens the Dimensional Holes, when Dusknoir arrived in the Hidden Land, via a Dimensional Hole, he is quoted as saying "I had Dialga send me here directly." However, Darkrai was also seen opening a Dimensional Hole without Dialga, so this point could be speculated.