First, some details on last night's game, since someone asked for it:
The party started in medias res, having just acquired a possibly magical silver orb engraved with hundreds of infinitely thin lines (after its owner, who was looking to sell it, has been killed in a freak tavern brawl) and on the way to Turin's Tradehouse, a colony in the Lowlands where someone might be able to tell them what powers it might have. However, they took a wrong turn somewhere (or the land has shifted again), and ended up in Stepstone Ford, a small hamlet of beehive-like stone structures on the edge of the Bitter Brambles. During their first night, a murder has taken place in the hamlet, casting some understandable suspicion on the travellers. In order to prove their innocence, they decided to head out into the Brambles in search of a mad hermit who lives nearby and was responsible for the theft of strange magical artifact whose function nobody knows four years ago - and who they suspect might be the murderer. In the endless sea of thorny vegetation they've first stumbled into a clearing full of dry sinkholes and strangling roots, then investigated what looked like some sort of plantation - where the Thornhorse mentioned earlier animated and attacked them. Killing it is where we'll pick it up next Sunday.
Now for something meatier: how to kill a Thornhorse (or anything, really) with a rhyme.
This spell has the power to give words a sharp magical edge to actually cut things with. It has two known uses:
1, By concentrating on a victim within sight, a sorcerer can prevent him from pronouncing a single pre-determined word: should the victim attempt to speak the word, he would start stuttering and coughing. He might say the word with considerable effort, but doing so will cause him 1d6-1 points of damage as the word cuts his mouth on its way out.
2, By delivering two (or more) lines of rhyming, metered and previously unused verse, the sorcerer can cast his own cutting words at a single enemy from a range. Damage done is determined by DM's discretion, but 1d6-1 would do for a rhyming couplet. (In last night's game, Qabar rhymed "burn" with something, so I gave it 1d6 damage because it was especially appropriate against a plant monster.)
As a note, this idea comes from historical pre-Islamic Arabic magic which I've studied for a semester. Just before battle, wizards would stand in front of the enemy army and shout rhyming curses - and the enemy would drop on the ground to avoid being hit by the rhymes flying through the air!