Magnus would likely use his powerful magic. He could create wards around the place where Harry is staying. These wards would be strong enough to keep out any dark wizards or creatures. He might also give Harry a charmed amulet that has protective spells on it.
One heartwarming scenario could be Magnus using his magic to create a beautiful, enchanted nursery for baby Harry. He could fill it with floating toys and a crib that rocks itself gently. Another might be Magnus cooking special baby food for Harry with a touch of magic to make it extra delicious and nutritious. Maybe he'd also read him magical bedtime stories that bring the pictures to life on the walls of the room.
One challenge could be understanding baby Raphael's needs. Since Magnus may not have had much experience with babies, he might struggle to figure out why Raphael is crying - whether it's because he's hungry, tired, or in need of a diaper change.
The story could explore the bond that forms between Magnus and baby Raphael. Since Magnus has such a long life and a lot of experiences, he would be in a unique position to shape Raphael's early life. He might tell Raphael stories of his adventures, and as Raphael grows, these stories could inspire him to be brave and kind.
Maybe it's the child of one of his friends or allies. For example, it could be the baby of Ron and Hermione. Harry would then be taking care of the baby out of loyalty and friendship.
Harry might first try to figure out what's wrong. If the baby is hungry, he'll quickly get a bottle. If it's a wet diaper, he'll change it. Sometimes, he just holds the baby close and rocks it gently, humming a little tune. He doesn't get frustrated easily because he really cares about the baby.
One possible plot could be that Harry discovers a time - traveling accident has brought baby Snape to his present. Harry, being the kind - hearted person he is, takes it upon himself to care for the baby. He has to figure out how to feed the baby, keep him clean and comfortable. Maybe he also has to protect baby Snape from any threats in the wizarding world that might target Snape even as a baby.
A heartwarming moment could be when Harry takes the baby out for a walk. He pushes the stroller carefully, talking to the baby about all the things they see around them, like the colorful flowers and the friendly squirrels. And at night, when the baby has a nightmare and Harry stays up all night comforting it. He rocks the baby gently and whispers soothing words until the baby calms down and falls back asleep.
In this fanfiction, perhaps Harry could struggle at first with the basic tasks like feeding and changing the baby. He might make mistakes but learn quickly.
One possibility could be that Draco is forced into taking care of Harry due to some magical circumstances. Maybe there's a spell gone wrong that makes it his responsibility. He initially resents it but as he spends time with baby Harry, he starts to see the innocence in him and develops a soft spot.