The Anga's Ruby ring is a quest reward. In the islands (western I believe) there is a cursed ship where you can take a quest. You must go to the temple of deceased souls in the marshan swamp and buy an indulgence for them. Not a good quest for a person who tries for a quick victory, but it's worth 4.5k XP and a great item.
Inquisitors are found in the greenwort, marshan swamp and in velarion forest. That's pretty much all you can get. Ther rest of it you'll get through sacrifice. At least I did...
I also think you should try and fight a bit more. In gray wasteland I'm close to 22 on impossible, and 19 seems a bit low to me, especially if it's on a lower difficulty, because on lower difficulties, it's easier to level up.
At this point, you must have at least 2 interchangeable strategies for the battles. At this point I'm going for a tank and multi-thorn strategy, both based on the target spell. Vs big packs of low-lvl units or Dragons I use Dryads + Thorns. Against packs of lvl 3-4 units I use emerald dragons + archmagi for a tank + shield. The dragon doesn't attack at all, save for the mana source talent.
Hope this helps... So far it does for me.
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