Seven:
The runes were drawn, the diagram was charmed straight, every detail was as perfect as Harry could make it. Even the summoning ritual's oddly specific descriptions for red chicken feathers here and greenish robin's eggs over there were laid out.
Thank heavens that no requirements from anything sentient had been called for. The-Boy-Who-Lived-Twice didn't want to consider himself depraved enough to even go that route to achieve his ends. He didn't think the people he was trying to help would even want that kind.
With one last, deep breath, and a tight grip on the Deathly Hollows, Harry began the invocation to summon Death.