There is a woman named Arvena Thelas in the town of Anvil who has four rats in her basement (the same as the first Fighter's Guild quest). If your level is high enough that rats do not cause you significant damage, you can break into her house, annoy the rats by punching them (or casting drain fatigue spells if your punch is too strong), then letting all four rats attack you while occasionally casting a heal spell. This is also useful for raising your Block skill, and is much easier than repeatedly causing summoned monsters to attack you.