Run around at certain distance and use fortress. Not too far becaus he jumps, not too close because you get meleed. Move to dodge baelfire.
Lion + lion helm.
Switch with slows target, tu axe is ok, but better something with at least 25% (boss slow cap). It lasts 30s, can't be overwritten if you switch to 0 slow main hand. So thats viable strat, switch for lets say LO runeword in random weapon for fortress to slow him, every 20-30s.
Using better weapon than TU labrys helps, but isn't necessary.