Terror vs. 63: (d100)[78]
Fortune: (d100)[6]
Horse, not sure what's the WP of a destrier: (d100)[6] - Most likely a success, even at -20.
Charm Animal 49: (d100)[12] - If Bastard passed his test, Elsa will use this test to help Tattie with her horse, since Tattie would be the closest character.
Fortune: (d100)[64]
I advise we perform no attacks against the wyvern unless it becomes clear that the wyvern is coming after us instead of, say, one of the bolting horses.