Every wand has a core, a substance from some magical creature that gives the wand its abilities to channel magic. It is unknown how many magical creatures yield wand worthy substances around the world. Mr. Ollivander chooses to use only unicorn hair, phoenix feathers, and the heartstrings of dragons, but other cores such as veela hairs, thestral hairs, acromantula webs, and basilisk skin are included in the list of possible cores. It cannot be said why exactly he chooses to use these three cores only, but many wandmakers choose to use a wide variety of wand cores.

       The core of a wand influences the personality of the wand. For instance, Garrick Ollivander would not use Veela hair to make his wands, as they tend to make rather temperamental ones. There is a very special case of wand core, being Thestral hair, as those wands work best with those who have faced death, just like those who are able to see the creatures from which the core comes.

       An interesting effect that comes from wand cores is when two wands have a core from the same source. These wands would be said to be brothers, and can result in Priori Incantatem if the wands were to come into conflict.

       Priori Incantatem, also known as the reverse-spell effect, is a magical phenomenon that happens between brother wands or is induced by the incantation 'Prior Incantato'. When this phenomenon takes place a golden thread of energy connects the tips of the two wands, while energy projections shoot out of that thread and encage the casters. They commence in a battle of wills, the losers wand being forced to project 'ghosts' of the previous spells it cast and ethereal projections of its victims.