Can you play Cull the Weak without controlling a friendly unit, and can you move Traveling Merchant with 0 cards in hand to still draw 1 card?

Ruling: Yes to both questions. You can play Cull the Weak without controlling a friendly unit, and you can move Traveling Merchant with 0 cards in hand and still draw 1 card.

Nuances:

• For Traveling Merchant, being unable to fulfill the discard requirement (having 0 cards) does not prevent you from resolving the draw effect.