The Red Diamond is a Mysticism and Restoration spell available in The Elder Scrolls III: Morrowind that allows the subject to reflect spell effects back at an attacking caster while simultaneously increases the value of long blade skill.
All effects are for 12 minutes on self:
This spell is not available for purchase in Morrowind or expansion packs. Although not intended for use by the Nerevarine, it can be acquired on the PC by using the console:
Player -> AddSpell "the red diamond"