The Trigger for this effect is the Permanent being Killed and sent to the Trash. 1. If the Permanent with the effect is not sent to the Trash, for example because its "killed" event was replaced with a recall, the Deathknell will not occur. 2. The trigger will be added to the chain as a Pending Item before the card with Deathknell is moved to the trash due to a Kill instruction or a Cleanup. 3. Before the card with Deathknell is moved to the Trash, note its location, its attributes, and any other details related to the effect of its Deathknell to process the trigger after it has been Finalized.