According to this a burning candle releases about 80 watts.

It could operate a Sterling engine .

Assuming most of the candle's energy is released as heat, with light and magic making up a small percentage, and assuming a perfectly efficient engine, and a spherical cow for good measure...

You could charge your phone, or a power bank. You could power a light bulb. You could heat up water (for a flow of 2 milliliters per second, you could raise the temperature by about 10 degrees Celsius).