MonkeyBoy does not survive. He takes 23 from the breath (rolled 17 Ref save), and the fall kills him. Lawful Good cheers the demise of the annoying MonkeyBoy. Plantagonox can breathe again next round. Plant' is at 80N80E40Z, southeast, with 126 HP.
Round 560: A huge, 15 foot tall equine creature with six muscular legs trots into the arena. It is covered in short white fur, and has two curving horns and two wickedly sharp tusks. It trots over to 75N90E and bellows, a horribly loud blast which stuns and deafens Plantagonox (rolled 20 Fort save). Plant' takes 18 points of damage from the fall, and is prone at 80N80E. Plant' has 108 HP remaining.
Round 561: Monster Horse stomps Plant' with two massive hooves, bites, and gores (worst roll 24) for a total of 58 points of damage. Plant' has 50 HP remaining.
Round 562: MH stomps and bites (worst roll 27), but misses with gore (natural 1), for a total of 39 points of damage. Plant' has 11 HP remaining.
Round 563: MH stomps, bites, and gores (worst roll 22) for a total of 53. Plantagonox is off to a far better place.
Next in round 563 for Lawful Good is a couatl (Expanded Psionics Handbook and Monster Manual). Its knowledge skills are history and nature, neither of which help to identify its opponent.