When someone superannuates, they retire from work, usually because they are old.
Superannuating is usually a happy thing because it means someone can stop working and enjoy their time.
Examples:
My grandpa superannuates from his job next month.
She superannuates after working for 40 years.
When he turns 65, he superannuates from his job.
The old dog superannuates from chasing cars.
In the story, the wizard superannuates from casting spells.
The superhero superannuates from saving the city.