Digimon Tamers (2001)

S1E44 The Messenger

A mysterious girl appears alongside her Digimon, Dobermon. They’ve been sent by Azulongmon to help the Tamers achieve Biomerge at the Mega level. It becomes clear that Dobermon is a precious gift, and he ultimately sacrifices himself to enable their digivolution. The Tamers learn that a significant portion of the D-Reaper is located in the real world, putting them in a critical position to prevent it from wreaking havoc.