lol.....I got stuck there too....as to the invulnerables....there are 4 of them, 3 cast the 2 turn spell on each other, save that Leandra does not cast it, so always 1 of the 4 (then 3, then 2) are invulnerable....once her last guy goes she puts up the 3 light pillars....attack them and you're good to go.