The bard is considered to be really unpredictable and his hugely powerful destructive effects can go either way. Furthermore, the destruction happens not by the bard's own will, but by the will of the aspect. You can choose to take "the will fo the aspect" literally or not but the implication is that the bard has little or no control over when destruction happens or what the object of that this destruction is. Calliope implies that it's a dangerous class to have around and expresses relief that there isn't one in the kids' session. Bardic destruction is portrayed as undiscerning between friend or foe and so powerful that it's likely to change how a session is going completely in one single moment (say, in a session with a Bard of Rage, everything could be lost because a being full of rage shows up unexpectedly in the last possible second and, for example, destroys the door to the universe your team created just as the team leader is about to touch the doorknob...). A Bard in your team can be very bad news indeed!UU: while the more passive bard coUld be seen as "one who allows x to be destroyed, or invites destrUction throUgh x," as if by the will of the aspect.
TT: I'm obviously no expert, but that sounds like a pretty odd thing for a Bard to do.
UU: maybe! it's a qUirky class.
UU: somewhat like a wildcard role for a hero. very Unpredictable.
UU: they are typically known for their spontaneoUs and dramatic story-altering inflUence on the fate of a party.
UU: some of the more remarkable tales involve sUch parties, where the bard is single handedly responsible for their spectacUlar downfall or improbable victory. or both!
UU: in trUth, yoU are probably fortUnate yoUr groUp doesn't have one. :u
TT: I think we have enough unpredictability as it is.
Of course, it could also mean that the Bard does have some control of his powers but he's more likely to have a whimsical and capricious personality, but I reckon that the unpredictability is part of the class mechanics, and that the destruction happens at random.
One does wonder if an extremely skillful Seer or a really powerful Player of Light could predict the effects of that destruction or make sure the destruction is channeled towards a victorious end.