For melee users... for me, this battle went from a little tough to quite easy by just slowing down. The temptation was to run in and beat the crap out of him as fast as I could, but I couldn't quite deal enough damage before he'd just heal up with his flask (he only has one though!).

What worked for me is to use a quick 1H weapon. I started the battle right behind him and got a free backstab in. Then I chipped away at him, rolling in or and taking a swipe (or jump attacking) until he got low enough to use his potion.. then just rinse and repeat. Jump attack works pretty well on him and actually manages to evade some of his swings in the process.

his AI can not handle a flail with Wild Strikes

Used Right Trigger attack with Battle Hammer. Pretty cheese way to kill him.

If you bow to Mad Tongue when he enters into the Hold, he will bow back at you giving you the Reverential Bow emote

If you don't hit him and wait for a bit, you get the reverential bow gesture

Stun locked with rapier. Need higher stamina

just spammed him with moonveil ability and dodge, pretty easy, 1 hit then dodge, repeat till he dies

I used Keen Uchigata +7 with Blood Resin for extra bleed and Unsheate. Backstabbed and then just went ham on him. Bleed pretty fast.

You can get your Runes back without fighting him by dying right up against the door to the right. You'll be able to retrieve them from the room down the stairs behind the Blacksmith.