Priori Incantatem

Copy target instant or sorcery spell, then return
it to its owner's hand. You may choose new targets
for the copy.
"The golden thread connecting Harry and Voldemort splintered; though the wands remained connected, a thousand more beams arced high over Harry and Voldemort, crisscrossing all around them, until they were enclosed in a golden, dome-shaped web, a cage of light..."