Does Deathknell trigger if a creature's death is prevented by Sett or Hourglass?

Ruling: No, Deathknell does not trigger when a creature's death is prevented by Sett or Hourglass because the creature does not actually die.

Nuances:

• Sett and Hourglass provide replacement effects that prevent the creature from leaving the battlefield or dying
• The creature gets healed back up or saved instead of dying