Do units with triggered abilities see themselves die and trigger from their own death (like Wraith of Echoes or Viktor)?

Ruling: Triggered abilities from permanents must trigger while on the board. Units cannot see themselves die because by the time they die, they have left the board and can no longer trigger.

Sequence:

• A unit with a triggered ability dies
• The unit moves from the board to the trash
• The triggered ability does not trigger because the permanent is no longer on the board

Nuances:

• Units can see themselves be played (entering the board) but cannot see themselves die (leaving the board)
• Deathknell is an exception because it explicitly triggers from the trash pile
• If multiple units die together (like Viktor dying with other units at a battlefield), Viktor will not trigger to create Recruits from the other units' deaths because Viktor has already left the board