DISCLAIMER: I do not own any of the characters, creatures, locations, etc of the Harry Potter franchise, they are owned by JK Rowling.
Xenophilius picked up his quill and parchment, and starting writing at his desk in his bedroom, with some difficulty due to occasional coughing fits.
My dear Luna,
In my old age, I find myself re-thinking my whole life, and I have realized something. You are right. The creatures I taught you about…they aren't real, my brain made them up for the things I didn't understand, mainly, your mother. The wrackspurts came from the feeling she gave me when I was near her, how my brain would stop functioning properly, I guess my brain decided she was just surrounded by wrackspurts. Nargles, how she stole my heart when we kissed under the mistletoe, I came up with the idea that they lived in mistletoe, and stole things. Crumple-Horned Snorkacks, well…I'll just point out the "Horn" part, and leave it up to you to figure out. The others I'm sure came about similarly. I do have a fascinating mind.
Luna, I'm afraid that this is the last time we will communicate, my time on this Earth is nearing its end, but do not be sad, for I am happy to go. I will finally be able to see her, after 35 long years, I will finally be able to see her…my darling wife. I'm sorry for leaving you, and Rolf and the twins. Give my best to them. You chose a good husband, and the twins are lovely grandchildren. Before I depart, I must admit something to you, something horrible. Back when the Death Eaters had you, during the war…your friends came to me for help, and I almost traded them for you. I was in a horrible time, I cared about you more than anything, you were my only family, and I almost betrayed everybody. You pick good friends well too, since they never told you, but you have to know. I'm sorry, I was stupid. I should have known they would save you.
Now my time here comes to an end. Farewell my darling Luna.
Goodbye, with love,
Your daddy, Xenophilius
Xenophilius looked the letter over, and then sealed it, sending it off to Luna. He then laid down on his bed, closing his eyes. When he awoke, he was not really awake, for he has passed on in his sleep, but the first thing he saw was his wife, and he smiled wider than he had since her death.