The boy who lived... come to die? (Harry Potter)
Solution 1:
I think the English (as written) is a bit ambiguous. It could be an ellipsis, as you wrote:
The boy who lived (has now) come to die.
or it could be a command
The boy who lived. Come (here), to die!
The tone of the speaker would probably make it clear. I feel that the if the speaker was speaking in the first case, the word "come" would probably be spoken more softly, whereas in the second case, "Come!" is a command and would be spoken more forcefully.
The trailer is here and it sounds to me like it's an observation than a command, so I think the first interpretation is correct.
Solution 2:
In the way it is written, it is in the imperative mood. The two sentences are grammaticaly separate:
- Harry Potter, the boy who lived (a different way of saying “Hello Harry”)
- Come to die!
With a different context, the present of the indicative mood could also be used, but the meaning would be altogether different:
(Voice-over) Harry Potter, the boy who lived, (pause for dramatic effect) comes to die
Of course, being the singular third person, comes then has a final s.