The first time Hagrid saw Aragog, he knew he had to have him. So he took the spider from the stranger whose pocket he had ridden in, and back to his dorm in the large stone castle. He couldn't help but think that something was wrong with Aragog, other than the fleeting feeling of familiarity.
Sometimes he thought he could remember another spider, large and fearsome. And a cliff, with a girl whose mind was just as monstrous and twisted as the creature whose company she kept. He think he loved this girl, once.
Hagrid has always dreamed of flying. When he was young and full of folly he fancied that he would one day grow wings and fly away. Then he was older and dreaming of cliffs and pain and girls with spider eyes made him wary of the sky. But the dreams were still there, in the corners of his mind like tattered cobwebs.
Sometimes he thinks that he can hear the creatures he works with talking to him. It is a whisper, barely there brushing against his mind. It reminds him, sometimes, of dreams he used to have of vast lands filled with creatures of fantastical forms, vast multitudes of white hide and scales and feathers.
In his dreams the whispers aren't whispers but true voices and he can hear them all, a cacophony of joyous sounds and vicious war cries. In his dreams he can feel them, each of them a brilliant spot of light, connected to him, circling him like a hundred thousand stars. In his dreams, he knows that he is not alone, surrounded by those stars. He feels their power, and he knows he could surround himself with the warm friendship of these creatures, feel the reassurance of their minds against his own, or lead them into battle and have his shining white army painted in all the lurid colors of his enemies. He thinks he's done it once-painted with those colors. Then he wakes up and doesn't know whether to laugh or to cry because he's Hagrid and there is no white army of beasts, no field of stars touching his mind and part of him knows that half of what he saw was never his dream in the first place.