DigiCore

A DigiCore (デジコア「電脳核」) is a type of nucleus that contains a Digimon's most important data. If that core is destroyed, the Digimon is usually deleted, though some may survive as spirits. It's a very powerful energy source, with each Digimon possessing one. The exceptions are the Digimon Sovereigns; Ebonwumon, Baihumon, Zhuqiaomon, Azulongmon, and their master Fanglongmon each possess 12 which surrounds their bodies, usually in a ring formation. Another digimon with multiple digicores happens when BanchoLeomon and Darkdramon jogress evolve to Chaosmon, where in such a case, instead of a fused digicore, the digicore of the 2 digimons remain separate. Gravimon, one of the Big Death-Stars, can remove its own DigiCore out of its body and place it in somewhere or on someone else for safekeeping. In some Digimon, the DigiCore has been corrupted and is called the "Dark Core". The Digicores have amazing power, as seen in Digimon Adventure 02, where Azulongmon gave Gennai one of his, which in turn allowed for Paildramon to become Imperialdramon for the first time. It also gave the original DigiDestined's Digimon the power to digivolve to their Ultimate level once again. Another one of Azulongmon's also allowed Agumon to digivolve to WarGreymon. Also, if one of the DigiCores are gone from one of the Digimon Sovereigns then the Digital World's defenses will weaken, making the Digital World unbalanced.

Black DigiCore
The Black DigiCore is an artifact that appears in Digimon Next. uses them to enslave Digimon and humans to his will by inserting them into the target.