The Sea of Grass — Gilbert M. Stack

Forbidden from returning to Aquila, Marcus Venandus responds to a plea from a half-brother he has never met to aid him in the far away land called the Jeweled Hills. When pirates shut down the sea routes the legion officer and his two trusted companions are forced to join a caravan to make the slower journey north across the treacherous Sea of Grass. Yet this may not prove to be the safer choice. A mysterious shaman has sworn to drench the plains in the blood of foreigners and his mastery over storms gives him the teeth to fulfill his oath. As chaos envelopes the trail, it will fall to Marcus to organize the defense and try to shepherd the frightened civilians of the caravan to safety again.