Cerberos

The dog that guards the gate of hell in Greek mythology. Just slap him around. Throw Holy Water on it to do some real damage (go on the pillars above and throw it onto him while evading his attacks). Due to it's size, it will have problems getting away...It's in the Abandoned Mines. Soul Steal isn't bad either. Trying to attack it continuously with your sword produces faster results, however it'll charge at you and most likely hit you more often.