The following article is about a fanonical concept.
It refers to recurring elements or tropes in Harry Potter fan-fiction.

The "magical core" is a fanonical concept, perceived by many members of the Harry Potter fan-fiction community as the origin of a magical being's power, and is used extensively in fan-fiction works to determine a wizard's power level, and to establish limits to a wizard's use of magic.

This trope usually comes accompanied by concept of "magical blocks", both frequently used in bashing fan-fictions.