Does Glasc Deathknell's ability work with Drag Under (i.e., can you play Drag Under on Deathknell)?

Ruling: No, Glasc Deathknell's ability does not work with Drag Under because Drag Under is not a unit and costs more than 3 energy.

Nuances:

• When determining if a card meets cost requirements for abilities, always use the printed cost on the card, not any reduced or altered cost
• This means even if you play a card with a cost reduction, effects that check cost thresholds use the original printed cost