Ballade; French. Twenty-eight lines divided into three octaves and an envoi (a quatrain in this case). Lines of any single length. Scheme ababbcbC ababbcbC ababbcbC bcbC with C being the refrain.

the envoi should probably encapsulate or reiterate the overall theme of the poem... it should bring it home to the reader in conclusive terms. So... the form is intended to pack a punch (as opposed to generating a feeling, as the rondel seemed to lend itself to).

Got it. If the envoi is intended as a slap in the reader's face, then the initial octaves should either A) build steadily towards the final theme in a relentless and incremental progression or B) (more difficult) move steadily around the theme, obscuring the final meaning until the envoi delivers it like an electrical shock.

With that in mind, the form lends itself to either the unexpected or the relentless. Death (of course) or the process of maturity. A trick. A practical joke or pun. A sudden twist, a sprained ankle. A ghost story. Just deserts.

Hmm. The form actually lends itself to a fairy tale. The standard three occurences, followed by a climax that touches on the same idea.