Nasak is an advanced sacrificial healing technique common to Phantasy Star games.
Phantasy Star series
Phantasy Star II
In Phantasy Star II, nasak costs 1 TP to cast. It fully restores the health of all party members at the cost of the user's life.
Phantasy Star III
In Phantasy Star III: Generations of Doom, nasak costs 1 TP to cast. It fully heals all allies in exchange for the user's life.