If I cast Void Seeker and my opponent kills the target unit in response with Hidden Blade, do I still draw a card?

Ruling: Yes, you still draw a card. You do as much of the card as possible when resolving it.

Nuances:

• You must have a valid target when initially playing Void Seeker (you cannot play it just to draw if there's no valid target)
• Unlike some other games, the spell does not "fizzle" entirely when the target disappears