Wuchang Fallen Feathers Master Raider Man eating Dhuntanga

I just started the game and kept going until I arrived at this boss, and got my ass kicked. I figured I was not supposed to fight this boss yet as I had zero upgrade to my HP, endurance or weapon. I did a bit of that in the area and went back to boss. I had already gotten to second phase so I knew I needed some fire mitigation/resistance but did not really have much gear choice. In terms of weapon, longsword seemed to work fine as its second hit grants ability charge. Getting behind the bosses somehow and doing a few charged heavy attack to break poise to do a lot more damage seemed to work well here.