This ability will enable Willow to give herself a particular mental immunity. For example, she could give herself immunity to having her mind read, or being controlled telepathically, or seeing telepathic hallucinations. When the immunity is activated, she will prove immune to the effects of any ability which tries to do what she is immune to. However, she won't be able to possess multiple immunities at once. When a new immunity is chosen, the earlier will automatically be lost. She also won't be able to change immunities too rapidly.