There are a couple merchants in the bunker at the start of the fjords, as well, after they surrender.
Do you have a bow? That might help take out ground opponents. Make sure you summon your creature, as well.
Send your runners out for diamonds and malachite ore, if you don't need anything for better enchantments, and whatever plants you need for the strongest healing or stat/armour boosting potions you have the formula for. A few boost potions before heading into a fight can make a significant difference.
The only other person you can trade with in the battle tower is Grim, on your necromancer's platform, but he only sells creature parts.
If you head back outside on Sentinel Island there are a few more opponents to take out. You might be able to level, in which case Sassan's inventory would be different the next time you talked to her, other than pre-set items and gold (save before approaching or talking to her and you could reload to see if she would offer you a better sword, though I don't recall buying anything from her). More importantly, there is a dragon skill book you can find in a nest in a tree outside, the boat in a tree containing the treasure Turgoyn wants (though you may want to use it yourself, rather than complete that quest), and a few chests with random loot.
