Cirri is a cat owned by Sara, who cooks at the Stag and Lion Inn in Baerlon.
The night Moiraine's party stayed at this inn, guests complained that several dead rats, apparently killed by Cirri, were found in the inn, all with their backs broken.
From Sara's comments about the unusual behavior, it seems likely that they were not killed by him as was assumed, but were instead killed by Ba'alzamon as a warning to Rand Al'thor.