Minerva’s patronus and her animagus forms are feline, always were, from the first time she cast the spells that now come so easily to her and she had no litter, bore no bairns of her own when it was possible. Now Tom Riddle may think he is the most important wizard ever to stride the corridors of Hogwarts and that he can return here to triumph, but Minerva has been in a good many Sorting Ceremonies and seen childish faces full of trepidation or hope walk towards the Hat after their names were called, she's seen the big, toothy grins as 'Gryffindor' or 'Hufflepuff' have rung out, the faint looks of doubt at other times, she has seen hundreds of children go to a table stacked with food, surrounded by older students there to let them know that it is now their table and that one day they will grow tall, their heads a little fuller of magical lore, the ones welcoming new students to their midst - and Voldermort means to stop all that by the foulest of means, does he? The mother bear in Minerva's breast rouses, and she casts the first of many protective spells, until the time comes for attack.