If Seth plays his legend ability to return a unit to base (instead of killing it), does Seth still draw two cards from Hidden Blade's effect?

Ruling: Yes, Seth would still draw 2 cards even if the unit doesn't die. The unit is still on the board when Hidden Blade resolves, so information about its controller is still available.

Nuances:

• The unit doesn't have to die for the draw effect to trigger
• As long as the unit is still on the board when the effect resolves, the controller information is available