Help with a Custom item

[Dragnmoon]

Is it possible to add this Item with it mention in my saves it gives a situation bonus? And How would I?

Basically it is an Item that does not need to be equipped only carried that gives you a resistance bonus equal to the number of remaining charges on saving throws against spells and effects with the death descriptor. It starts with 5 Charges.

Charges once used are gone and can not be renewed, similar to a wand.

I am trying not to to be too spoily.