REDU format ruling
Yubel - Terror Incarnate

Nearest-era rulings (Tengu, Sept 2011) — no REDU-specific archive exists.
Card effect (current official text)Cannot be Normal Summoned or Set. Must be Special Summoned by "Yubel", and cannot be Special Summoned by other ways. This card cannot be destroyed by battle. You take no Battle Damage from battles involving this card. Before damage calculation, when this face-up Attack Position card is attacked by an opponent's monster: Inflict damage to your opponent equal to that monster's ATK. During your End Phase: Destroy all other monsters on the field. When this face-up card leaves the field: You can Special Summon 1 "Yubel - The Ultimate Nightmare" from your hand, Deck, or Graveyard.
Rulings
- Destroying all other monsters during the End Phase is a Trigger Effect.
- When a face-up Yubel - Terror Incarnate is sent to GY, removed from play, or returned to its owner's hand, its effect to Special Summon Yubel - The Ultimate Nightmare activates. This effect cannot be activated when it is returned to its owner's Deck.
- When Yubel - Terror Incarnate is removed from the field, its owner activates its effect. (If your opponent controls your Yubel - Terror Incarnate when it is removed from the field, you get the effect, not your opponent.)
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the REDU forum — sourced change requests get reviewed.