THE EARTHQUAKE OF METAL GREYMON
(Episode 20)

The kids go after Datamon, who has kidnapped Sora and Biyomon. 

While the others provide a diversion, Tai and Agumon enter his pyramid, where he's trying to make a copy of Sora.  Tai and Sora are able to get away when Etemon and his forces burst in to attack Datamon. 

Datamon tries to drop Etemon into a black pit, but he, the pyramid, and Etemon's forces are dragged in, too.  Etemon manages to escape and prepares to attack the kids.

Fortunately, Greymon successfully digivolves to his ultimate form, Metalgreymon, and is powerful enough to defeat Etemon. But as he does so, he and Tai are dragged into the black pit -- a dimensional rift.