Implode (Fire) reads: "Highest health enemy in play is destroyed".
I believe it used to read differently, and the current reading suggests it will not target one's own forces. However, this is not the case.
I do not recall seeing any changes to the way Implode works listed in any of the upcoming changes threads, so I assume it's supposed to still be able to destroy one's own forces. If this is not true, the card isn't working properly (killed my own Stormship instead of my opponent's lower health minions). If this is true, it ought to be reworded to indicate that one's own forces are vulnerable to its effect.