From LSWiki

Class: Psionic Skills
Attribute: Willpower
Pedagogy: Body Alteration
Practitioner Term: Somatopsychotic
Specialty Required: Degree I
Hidden Skill

This skill represents an infusion of psychic energy into one's body, replacing natural substance with psionic essence, making one
resistant to the influence of such forces, potentially even to the point where exposure that would have been harmful is instead
restorative.  Strangely, the somatopsychotic even displays a slight resistance to the inutterably powerful divine and primal
energies.  However, the more one relies on psychic energy for one's existence, the more vulnerable one becomes to magickal,
spiritual, goetic, and oneiric energies.

Somatopsychosis can be increased by exposure to vril, divine will, or quintessence, as well as degraded by exposure to magick,
theophany, dream, or ectoplasm, changing more quickly according to one's somatic adaptability.

Notes

• Suggestion for this is to get it to 5-6 range and become immune to all psionics and then face-roll mobs such as Vlekthid, Gogtzul and even Cthulhu. Minimal to no risk, just make sure you can do damage to them.
• Accessible through various guilds and assocs, easiest being Touched

Trainers