When Nathan had found out that Delphi didn't know how to produce a Patronus, he insisted he help her learn how to. It would be fun, Nathan said. No pressure, either.

"Remember, think of the happiest memory you can, and hold on to it." Nathan instructed patiently, as Delphi prepared herself, wand at the ready - pointed at a defense dummy.

Delphi gave a slight nod, as if to say she was ready - and closed her eyes, thinking. Her eyes fluttered back open, her wand raised, "Expecto Patronum!" She exclaimed, and watched a silver swan emerge from her wand.