This optional boss in the Iron Keep is sure to give you a bit of a tough time. During two separate parts of the fight, he powers up and becomes even stronger. The first is when his chest erupts in flames, the second when he lights his sword on fire, imbuing its attacks with additional magic damage.
This encounter is all about roll dodging his attacks and getting in a bit of damage when you can. For more specific tips for dealing with his moveset, take a look at the video above.
For more help be sure to check out our complete Dark Souls 2 Boss guide.