1. Portal damage mitigation. With 0 ranks Mentus an exile's health is taken down to where they are "red", with 20 ranks of Mentus, an exile is undamaged. Seems to be linear between, such that 10 ranks gives half the protection of 20 ranks.
2. Deadly poppies have no effect if you have at least 20 ranks of Mentus.
3. Shieldstone breakage is less frequent with Mentus training. With 0 ranks of Mentus, a shieldstone breaks about once every 50 times it is used. With 1500 Mentus, a shieldstone breaks about once every 500 times it is used. The amount of reduction with more modest ranks of Mentus is unknown, but it is probably an exponential (not linear) relationship, where the first ranks of Mentus give more benefit than the later ones.
4. EP Stone breakage is less frequent -- anybody ever verified this?
5. Illusion breaking... what is the range of Mentus values which are useful for this?
6. Cloud driving... can this be done by a non-mystic with sufficient Mentus ranks?
7. Reduction in amount of experience needed to gain a new rank -- anybody ever verified this?
8. Helps with PF path learning and remembering -- anybody ever verified this?