Can Zaun Warrens trigger if you have no cards in hand?

Ruling: Yes, Zaun Warrens can trigger even if you have no cards in hand. You do as much as you can, following the instructions in order.

Sequence:

• Attempt to discard a card (if you have no cards, you can't discard)
• Draw a card

Nuances:

• This principle applies to similar effects: if an effect instructs you to discard then draw, you'll discard as many cards as you can and then draw the specified number of cards