Can you cast Void Seeker without a target unit on the battlefield to just draw 1 card?

Ruling: No, you cannot cast Void Seeker without a valid target. The spell requires all targets to be present when cast, and Void Seeker does not have an "up to" clause that would allow targeting 0 units.

Nuances:

• If you cast Void Seeker with a valid target, but that target is removed (e.g., retreated to hand) before the spell resolves, you will still draw the card.