Mental Resistance

Mental Resistance is described on B81 and requires a "purely mental threat".
It is a variety of Resistant from B80
"except that the bonus applies to resistance rolls against IQ and Will instead of HT"
Resistant to Psionics is listed as the only example, a Very Common category.
Another possible (and probable) aspect of MR (though it is not explicitly stated) is that this could be considered a mental advantage by default instead of a physical one. If not, then it may be mandatory to add something like "requires will roll" to force it to become one.
There does not appear to be an explicit Mental Susceptability variation of Susceptible though, even though it inverts Resistant in many respects. Some other disadvantages have functions like that though.
category:Advantages