Magus of Echoes

When Magus of Echoes enters the battlefield,
choose a player. Whenever chosen player casts an instant or sorcery spell, each other player may
copy that spell and may choose new targets for
the copy he or she controls.
Are the future and the past really so different? If one
were to travel the opposite way on this timeline, would
the past be the future and the future be the past? Only
echoes exist to give us these answers.