Soul Core (ソウルコア), represented by 
, is a game mechanic which debuted along with the Battle Spirits Burning Soul anime. Soul Core is a special core that replaces one of the four starting reserve core. It can activate special effects of spirits or nexuses when used for leveling, and can activate additional effects of magic when used to pay the cost.
Soul Core is targeted the same as regular core by removal effects. The owner of a spirit being targeted by core removal can choose which core are moved. In addition, during the main step, spirits with only one core can switch core simultaneously between them without being depleted.