How Do Wands Work In Harry Potter?

"The wand chooses the wizard, Mr. Potter," Mr. Ollivander tells Harry. "It's not always clear why." 

Harry Potter's first visit to Ollivander's wand shop reveals that wizards don't wield any old wand. Instead, they use a specific wand that is a special match. Instead of the wizard choosing a preferred wood, core, and length, the wand picks those qualities to make the perfect match.  

The double-edged sword of this piece of lore is that children with parents who can't afford to purchase a new wand might inherit an old one from another family member. This sets them up for failure early on, as seen in the tribulations of Ron Weasley and Neville Longbottom and their inherited first wands. 

Ron's first wand was especially bad, according to Ollivander, because an "ash wand cleaves to its one true master and ought not to be passed on or gifted... because it will lose power and skill. This tendency is extreme if the core is of unicorn." Sadly, Ron's first, hand-me-down wand (from his brother Charlie) was an ash wand with a unicorn core. 

A core is the magical power source for a wand, and any number of magical materials will do the trick. For example, some wands have used wampus cat hair, jackalope antlers, and basilisk horns (in the case of Salazar Slytherin's wand). 

Young wizards who travel to Ollivander's for their new wands, however, are presented with only three core possibilities: unicorn hair, dragon heartstring, or phoenix feather. What they, and more casual fans of the franchise, might not know is that many more choices for wand cores are available; Ollivander just chooses not to supply them, focusing instead on what he refers to as the "supreme cores." 

Ollivander's father used "lesser cores" like kelpie hair for his wands. Throughout his life, Ollivander watched his father struggle with these cores, so he dedicated himself to experimenting with and discovering the finest wand cores. 

Because wands' magical qualities comes from their "cores," wands are described as "quasi-sentient," meaning they sort of have a mind of their own. "They're not exactly animate, but they're close to it," J.K. Rowling said during a PotterCast. "As close to it as you can get in an object because they carry so much magic."

A wand's sentience appears most prominently in its allegiance to its wielder. As Ollivander states in Harry Potter and the Sorcerer's Stone, the wand chooses the wielder. It also chooses whether or not to change its loyalty, and sometimes will do so if its wielder is defeated in battle. 

Some wands eventually lose their magic and refuse to perform any longer in a process known as "wilting."

Wands made from hazelwood are so emotionally connected to their owners that they will wilt after the person's passing. Sycamore wands, made for adventures and "questing," will occasionally wilt in spectacular fashion by bursting into flames once their owners grow up and settle down. 

Occasionally, a wizard will choose to extract the core from their wilted wand and place it in a new casing.

A wand's temperament and characteristics are dependent on the core inside it. The phoenix core, which Harry has in his wand, is known to be capable of the "greatest range of magic." According to J.K. Rowling, phoenix-core wands "show the most initiative, sometimes acting of their own accord."

The allegiance of these wands is "hard-won," making them the most difficult wands to tame, perhaps because the phoenix is an extremely independent, isolated bird.

Dragon heartstring is considered the most powerful core. Hermione Granger, for example, has a dragon heartstring wand. These wands, like Hermione, tend to learn more quickly than their peers. But because of that speed, dragon heartstring is the core most prone to accidents.

It's also the easiest core to be tempted by the dark arts.