Rats are a ubiquitous enemy in Evermore, appearing in all regions except Prehistoria.
Rats have a chance to inflict plague with their normal attacks, but otherwise are a mere nuisance; they have low HP and power, are very small, and move very quickly in erratic patterns, making it difficult to pin them down.
The Rat gives very little experience or money. However, it's very low HP and the fact they appear in large numbers when they appear makes them fairly effective for levelling up alchemy and weapons. The Hall of Collosia and Ebon Keep Castle are particularly good for this; the player can kill off the many Rats they find, and easily leave and return to the area to respawn them.