Aventus Aretino is a Nord child in Windhelm found in the home of his deceased parents. When found, he is performing the Black Sacrament, hoping to contact the Dark Brotherhood. Desiring the death of Grelod the Kind for mistreating her charges at Honorhall Orphanage, he asks the Dragonborn to fulfill the contract. If successful, he gives them the Aretino Family Heirloom.
Aventus lost his mother, Naalia, when he was roughly ten years old; the fate of his father is unknown. Because he had no one else to care for him, Jarl Ulfric Stormcloak sent him to Riften to live at the Honorhall Orphanage. At the orphanage, he developed a strong hatred for the headmistress Grelod the Kind, who, despite her name, was extremely cruel to him and the other children. Aventus escaped from the orphanage and returned to the now-deserted house in the middle of Windhelm, where he had lived with his mother when she was alive. When the Dragonborn encounters him, he is attempting to contact the Dark Brotherhood by performing the Black Sacrament.
In the Dragonborn's travels, a rumor is heard about a child in Windhelm that is trying to contact the Dark Brotherhood. This rumor can be heard from multiple sources, including innkeepers and guards. Upon hearing this rumor, the miscellaneous objective "Talk to Aventus Aretino" begins. Upon reaching the Aretino Residence, a child, Grimvar Cruel-Sea, can be seen asking Idesa Sadri if it is true that Aventus is trying to perform the Black Sacrament. Idesa tells him that this is nonsense, but when Grimvar says that he is going to go ask Aventus to play she quickly admits the lie and begs him not to approach Aventus:
Idesa: "Oh, Grimvar... always with the nonsense. No, no, of course not. Those are just tales..."
Grimvar: "Fine. Then I'll invite him out to play. He lives right there. I'm going to knock on his door..."
Idesa: "No, child! Wait! That boy, that house - they're cursed."
Grimvar: "Ha! Then I'm right. I knew it. He's trying to have somebody killed!"
Idesa: "All right. I won't deny it, child. What you heard is true. But Aventus Aretino walks a dark path. His actions can lead only to ruin. Now, enough. We will speak no more of this. I am the only friend you need.
Upon entering the house, Aretino chants the prayer to the Night Mother repeatedly while stabbing an effigy made up of human parts as he pleads for the Night Mother's help. No matter what is said, Aventus is sure that the Dragonborn has come to fulfill the contract if he is spoken to, and the quest "Innocence Lost" begins.
"It worked! I knew you'd come, I just knew it! I did the Black Sacrament, over and over. With the body and the... the things. And then you came! An assassin from the Dark Brotherhood."
- I'm sorry, boy, but I'm not who you think I am. "Of course you are! I prayed, and you came, and now you'll accept my contract."
- Yes, of course... The Black Sacrament... "It took so long. So very long. But now that you're here, you can accept my contract."
- (Remain silent) "You don't have to say anything. There's no need. You're here, so I know you'll accept my contract."
"My mother, she... she died. I... I'm all alone now. So they sent me to that terrible orphanage in Riften. Honorhall. The headmistress is an evil, cruel woman. They call her Grelod the Kind. But she's not kind. She's terrible. To all of us. So I ran away, and came home. And performed the Black Sacrament. Now you're here! And you can kill Grelod the Kind!"
- Assassinations don't come cheap, boy. "I have a family heirloom you can have. Supposed to be sort of valuable. I hope that's all right."
- Tell me about your mother. What happened? "She got sick, last winter, when the snows came. And she just... she never got better. Not all year. One night she fell asleep and... never woke up. So now I'm all alone. And the Jarl said I had to go to Honorhall Orphanage. It's not fair!"
- Are you sure about this, boy? Murdering this woman? "I've never been more sure about anything in my entire life. Someone like Grelod doesn't deserve to live one more day. She's a monster."
"Well? Grelod the Kind. Is she... you know?"
- Grelod the Kind is dead. "Aha! I knew you could do it! I just knew it! I knew the Dark Brotherhood would save me! Here, just like I promised. This should fetch you a nice price. And thank you. Thank you again."
- "Really, I mean, I knew the Dark Brotherhood was good... just not that good! You killed the old hag before I even asked!" – If Grelod is killed before talking to him.
- "I'll go back to the Orphanage in a while. I'll give them time to, you know... clean up the mess." – After completing Innocence Lost
- "When I grow up, I'm going to be an assassin. That way I can help lots of children, just like you." – After completing Innocence Lost
- "You came to visit! It's so much better here with Grelod gone. Thanks to you." -In Honorhall Orphanage after completing Innocence Lost
- "Sweet mother, sweet mother, send your child unto me for the sins of the unworthy must be baptized in blood and fear." – Repeatedly, until the Dragonborn interacts with him.
- "I'm so tired..." – Between bouts of praying and stabbing.
- "So... very tired..." – Between bouts of praying and stabbing.
- "Die, Grelod. Die!" – Between bouts of praying and stabbing.
- "Grelod, you old crone. You'll get what you deserve. The Dark Brotherhood will see to that..." – Between bouts of praying and stabbing.
- "Please... How long must I do this? I keep praying, Night Mother. Why won't you answer me?" – Between bouts of praying and stabbing.
- "You came to visit! So much better now that Grelod's gone, thanks to you!" – If another Aretino spawns in the orphanage.
- "No! It's not supposed to work like that!" – If the Dragonborn attacks him before talking to him.
- Despite being a Nord, Aventus is sometimes referred to as an Imperial by others, as his name is constructed like an Imperial one.