Supposedly destroying a pillar removes his immunity to that element, but I wasn't sure if that was true, and since I had him almost down on my previous attempt, I decided to just wear him down. It took forever on easy, and used a lot of pots.
I have only 2 chars that can do physical damage, and one of them was pure melee (madora of course), and just getting her over to him past the environmental stuff was gdam ridiculous.
The length of how long it took to kill him (restarting once due to dead chars not getting xp) is what I don't like about this.