Ring of Pain

Reflect is a rare effect, the easiest way to get it is probably with the Spiked Shield. Find it in blue/rare chests. It will deal 5 damage on parry. Once equipped, you just need to parry enough creatures where the reflect damage kills them.
Make sure to build up a decent amount of defense to make parries happen more often.
Also, if your attack and speed is too high that they do not get to attack you before they die, just pass the creatures to get them to attack you without you having to attack them