Arietis fled Kitalpha by way of boats on the Mossflower River, and was lying injured in the woods when she met back up with Rigel and Hollyfire. When the squirrels got to Mossflower Woods, it was Arietis who recognized it as such.
Arietis went scouting along the Mossflower trail and brought back word that Redwall Abbey was just a few days ahead. She was the first of the band to sight the giant Abbey.
While the band was packing up, Arietis mentioned that Digclaw would probably eat more than Rigel. This upset the squirrelchief, and the two tusseled. Near the end, they were revealed to be surrounded by otters.
When River's band met up with Rigel, Ivy recognized Holly, and, startled, Skipper acted like lightning and sunk his javelin into Arietis's chest. She was gravely injured, and was taken to Redwall Abbey immediately, where she was tended by Plithie Dormouse. Later, she died and was buried by Rigel, Hollyfire, and Digclaw. Her grave was made by Skipper and Log-a-log. It reads, Here lies Arietis Mistmint, wife to Rigel Squirrelking and step-mother to Hollyfire Squirrelqueen. Rest in peace, Arietis, you made it to Redwall from your destroyed home.
Later, Arietis went with Schedar on his second visit to Alrescha, warning her that Hollyfire would wreck revenge on her. Arietis was the one that reminded the wildcat that she had killed Holly's original mother, Kuma.