Permanent disablement cover provides a lump sum payment in the event of you not being able to work in your own or any occupation ever again.
Imagine the significant financial impact if you were never going to be able to work in the future. Not only that, but think about all the extra ongoing or specific care that you may also require.
You can use the benefit to pay off debt or cover ongoing living expenses. The purpose of the funds is entirely yours to decide.