Lucy's magic cordial is a gift from Father Christmas in 1000 NT. It's made from the flowers of the Fireberry, and has the power to heal the sick and injured. She first uses it on Edmund after the White Witch mortally wounds him in the first Battle of Beruna. After that, she uses it on a number of occasions, including curing Eustace of seasickness, healing Reepicheep's battle injuries and mending Trumpkin's old battle wound.
After she leaves Narnia, her cordial is given a place of high honor and is kept as an ancient treasure of Narnia.