If Void Seeker fails to kill something or its target becomes illegal, do you still draw a card?

Ruling: Yes, you still draw a card. The draw effect is not conditional on killing the target or the target being legal.

Nuances:

• Riftbound doesn't have "fizzling" - spells always resolve to the best of their ability unless directly countered
• Even if the target becomes illegal (e.g., with a flash effect), Void Seeker still resolves and draws a card
• The only way to prevent the draw is if the spell itself is countered