Tengu format ruling
Tragedy

Card effect (current official text)When a face-up Attack Position monster(s) your opponent controls is changed to face-up Defense Position: Destroy all Defense Position monsters your opponent controls.
Rulings
- You cannot activate Tragedy during the Damage Step.
- You can activate Tragedy after an Attack Position monster is changed to Defense Position by a card effect, such as Enemy Controller or Stumbling.
- Spear Dragon changes its battle position at the end of the Damage Step, so you cannot activate Tragedy at that time. Goblin Attack Force and Giant Orc change their battle positions at the end of the Battle Phase, so you can activate Tragedy at that time.
- Missing the Timing: The position change must be the last thing to have happened. If "Zero Gravity" was activated as Chain Link 2 or higher, you would not be able to activate "Tragedy".
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Tengu forum — sourced change requests get reviewed.