Symphonic Echoes and Undead

I just fought with a bard who somehow managed to distort my undead. I thought that was not possible, considering the nature of the the unliving. Is this a bug, or by design? Your infernal power EVISCERATES a young storm! You try to attack some empty air near a young storm. A flesh golem's smash MUTILATES a young storm! A zombie of a war-weary storm giant tries to attack some empty air near a young storm. A zombie of a war-weary storm giant tries to attack some empty air near a young storm. A zombie of a war-weary storm giant's punch devastates a young storm! A zombie of a war-weary storm giant's punch maims a young storm! A zombie of a war-weary storm giant tries to attack some empty air near a young storm. A ghoul's claw maims a young storm! A zombie of a war-weary storm giant tries to attack some empty air near a young storm. A zombie of a war-weary storm giant tries to attack some empty air near a young storm. A zombie of a war-weary storm giant's punch devastates a young storm! A young storm is DEAD!! You receive 0 experience points. A young storm's leg is sliced from his dead body.