The Leonal got dismissed by the planetar who summoned him because the planetar was confused (by an earlier chaos dragon) and the roll came up "attack nearest." The leonal, for good or bad, was nearest. The other planetar's SMIX spell was aborted also due to confusion. I haven't bothered with implosion yet because that's a really terrible 9th level spell. Slay living would be better because (1) at this level, the creatures pretty much need a 1 to fail anyway, so the DC is almost immaterial, (2) at least slay living does damage on a failed save. Why doesn't implosion?
In fact, chaos dragon's confusion has been the only serious threat to a group of 3 very old radiant dragons, a throne archon, two planetars, and a
t'uen-rin (who gated them all in).