Yuyutsu
Dungeon Spirit
I'm a pretty slow, bad spriter, so I probably won't be adding a wide variety of accessories like this unless someone wants to create sprites for them. Your example accessory would be pretty easy to code.
I really like debuff vulnerability as a mechanic, and will be working on adding these in for the next update.
Now, i'm not the world's best spriter, but I would really enjoy making sprites for you. I don't have too much experience, so you can definitely choose not to use my sprites, but I could make you a few sprites if you'd like