My battle set is a bit haphazard because I've found several things lying around in treasure chests and galleries. I need some final advice. What I have at the moment -

Phoenix Quill Trident Of The Banished One Rainbow Vortex Soma Tablets Gate Keeper Collar of Slavery Panzer Hydra Blade Shinwas Heart Pendant (which now needs to be replaced with something)

Scrolls -

1 X Cobalt Eternal 1 X Morosbane 1 X The Void Assassin

My pet has 13 AP left.

EDIT - I've now added an Item Hunters Bomb

Your set looks pretty good to me. The Phoenix Quill and Soma Tablets are staples. The Trident is a really god attacker to have. The Gatekeeper Collar is also fine for now and the Rainbow Vortex is nice to have. I don't know the exact stats of the Panzer Hydra Blade, but I think it's probably fine. A bomb is indeed a nice addition to your set.

It's always nice to have a laying around in case you want to blast two weapons. I always liked the for tier 7 since it has a pretty good heal, but if the Panzer Hydra Blade heals, then you probably don't need it. The is a pretty decent attacker, but doesn't have a heal. I'm not sure whether you really need it, since you have a couple of attackers already. For the long term, it might be nice to look into the in case you need another (near) full heal. And for future boss battles, another full block could be nice:

I would try to get an infinite use healing scroll, since the assassin scroll has a chance to do a negative heal. It might be nice to have a consistent heal, I'm not sure though, since I never used it, so I don't know how often the negative heal occurs. You could look into an maybe.

Thanks for your comments and suggestions.

I unequipped the Cobalt Eternal and added a Gift Of The Forj because somebody recommended it in another topic and there was one for sale.

The Panzer Hydra Blade does 8% heal.

I've never had any problems with the Assassin's negative heal but it has a chance to freeze.

Will look into some of your suggestions but a lot depends on if the items are available to buy.