My Darling Ari,
Oh, child, you did not understand. You never understood, and so your life was cruelly taken from you.
I know now. It dawned on me—it doesn't matter who killed you, my darling, the only thing that mattered, then and now, is that you are gone. Yet still I have found out, using careful memory skills and otherwise logic, and my conclusion is sure: I cast the spell. Albus, bless his heart, mind, and soul, could not have possibly done it. He is too pure of heart to ever have killed a poor, innocent little girl. And Aberforth, you see, probably was unaware such a spell could be cast—and he never would have done it, much less known how. And so, my dearest darling, you will find the answer in my very own words: I killed you.
Merlin knows I have killed other innocents, and I dearly wish you will pardon me my sins and give me the childlike love you once did, my dear.
And now, in writing (as I pen this in my prison, my very own prison), I have admitted to a fault, and may die happily (though Hell has saved a place for me especially, I'm sure). May Merlin bless you, and Albus, whom I have heard entered immortality much too recently. My heart is with you both, and my dearest wish is that my body will be, too, soon.
Love,
Gellert
A/N: Maybe I'm morbid, but I've always wondered who killed Ari. This simply had to be written, and I do hope you like my Gellert. For the Letters from (or for, in this case) Heaven Challenge, my second response. My apologies about the length. Please leave a review!