If using Imperial Decree, does a unit with damage counter die?

No, a unit with existing damage counters will not die simply because Imperial Decree is played.

According to RiftJudge FAQ #8633, Imperial Decree only kills units that take damage after the card resolves. It does not look back in time to kill units that were already damaged before the effect became active.

Here is the breakdown of how this works:

  • "Takes damage" refers to the event: The trigger condition for Imperial Decree is the event of receiving damage, not the state of being damaged.
  • No retroactive effect: If a unit already has damage counters on it when Imperial Decree resolves, it has not "taken damage" while the effect was active, so the trigger does not fire for that unit.
  • Future damage: If that same unit takes additional damage while Imperial Decree is active, the trigger will fire at that time, and the unit will be killed.

This is also supported by RiftJudge FAQ #2873, which clarifies that Imperial Decree does not look back in time to kill units that were previously damaged.