Wilhelmina Vandom is the daughter of Thomas and Susan Vandom. The couple had divorced and Will lived with her mother in Fadden Hills. When Will first caught glimpse of her mind-reading powers and saw the other girls talking negatively behind her back, her mother decided to move them to Heatherfield. Will is enrolled in Sheffield Institute and meets and befriends Taranee Cook, another mover to Heatherfield. The two then befriend Irma Lair, Cornelia Hale, Hay Lin, and Elyon Brown. At the Halloween dance night, the girls were saved by Taranee's powers when the bully Uriah Dunn pulled a firecracker prank. When the girls met at Hay Lin's house to discuss their strange dreams, her grandmother Yan Lin revealed to them the legend of the Guardians of Kandrakar and that they were to be the next generation. Will was entrusted with the Heart of Kandrakar. Her powers would come to bloom when two of Phobos' henchmen attacked her, Irma, and Hay Lin and they involuntarily transformed into their Guardian forms and fought them off. From that moment on, W.I.T.C.H. would be formed with Will as the leader and Keeper of the Heart of Kandrakar.
As the fifth Guardian, Will controls the power of Quintessence, the fifth element. Quintessence manifests itself as whitish blue lightning that she can use to fire offensive blasts and project defensive shields out of the quintessential energy. By using her power of Quintessence, Will can make inanimate objects come alive and act on their own accord but under her control by imbuing them with the same energy. In the case of electronic machines, Will is actually able to talk to them, and most of her own appliances have continuing minds of their own, literally. Will is still inexperienced in the controlling inanimate objects aspect of her powers. Will's secondary power is a utilization of her power of quintessence and bringing technology to life so she can talk to them and they can talk back but with distinct personalities.
As the Keeper of the Heart of Kandrakar, the physical embodiment of Kandrakar AKA the Heart of Infinity's power, Will has the power to channel the magic of the Aurameres into the Heart and therefore enter the Guardians, amplifying their powers and transforming them into their Guardian forms with colorful blue and pink costumes, different hairstyles, and pixie-like wings which they can all use to fly. Will can use the power of the Heart to close and, further down the line, open holes in the Veil, release a blinding pink light from the Heart, project a force field of pink energy, create numerous fake copies that would disappear in a flash of light, reveal the true form of another, locate other Guardians using their Aurameres and show images of places and people. The Heart of Kandrakar has a tel-empathic connection with Will. It's able to instinctively respond and act on its own will when the Guardians are in danger and can absorb, activate, and merge with other magical items. When the Veil was taken down, Will soon learned how to open folds in space and time to traverse different dimensions.
Will has displayed the power of superhuman strength and toughness on several scales. She's able to use a tree like a baseball bat and catch a falling catapult like it was a football and has a sensitivity to magic and supernatural writing and phenomena. She has empathic abilities with animals, as they seem to reflect her mood, and has a natural affinity for teletransportation, being the first to wield this universal Guardian ability.