If the target fails her saving throw, she contracts mindfire. The disease has no incubation period; the victim immediately takes 1d4 points of Intelligence damage. Each day thereafter, the victim must succeed on a Fortitude saving throw (DC equal to the manifested power's DC) or take another 1d4 points of Intelligence damage.
If the victim makes her Fortitude save for two days in a row, she fights off mindfire and recovers, taking no more damage.
For every 3 additional power points you spend, the disease deals 1 additional point of Intelligence damage, and the save DC (for the power and the disease) increases by 1.