Blue Card

The Blue Card appears throughout Digimon Tamers and Digimon World 3.

Digimon Tamers
Created by and delivered by the DigiGnomes, the Blue Cards are responsible for the creation of  and the bio-emergence of  and.

When Takato, Henry, and Rika used their Blue Card, it transformed their card readers into D-Powers, and allowed each of their Digimon to manifest in the Real World. Later, the Blue Cards allowed the Tamers to draw upon the power of and matrix digivolve to Ultimate. Although the first few Blue Cards appeared randomly, the Tamers are eventually able to transform their own cards into Blue Cards at will, though they usually use Evolution cards. Even Kazu's fake Blue Card works, because it draws on Takato's faith and Calumon's power.

Digimon World 3
The Blue Card is used to go between the east and south sectors. When you talk to the tricky Guilmon he will give you a false blue card called a 8lue card when you talk to the tricky Guilmon again in the basement of the forest inn he will give you a real blue card.