How does the Elder Scrolls 5 join the Dark Brotherhood?

1, get sideline tasks with Aventus first? Eretino, talk to me.

2. Find Aventis' house in Helmet City and pry it open.

3. Find another task after the conversation.

4. Go to Aventis' house to get the note after completing the task.

5. Talk to astrid and kill those prisoners.

6. Talk to astrid again.

7, and then go to the dark brotherhood shelter to join.