Thank you for trying my game and for your feedback. It means a lot to me!
In fact the Wizards can drop randomly a bomb, which explode when you fire at it (if you had an extra shot at the wizard, then it blows the bomb). The wizards' ability is to resurrect fallen fellows, if you let them enough time to cast their spell.
True: the explosion VFX is awful: I admit :) . I'm not good at art and hadn't time enough to find a good asset or tutorial...