Using a wish spell Xoots was granted a 4th attunement slot, this slot is permanent.

I was able to attune to this 4th item via a wish spell. I am now permanently attuned to this mask, if I am ever unattuned to the mask it will cause me to take an immediate indefinite madness, which will then compound if I remain unattuned to the mask over time. Once reattuned the madness will end