REDU format ruling
Green Baboon, Defender of the Forest

Nearest-era rulings (Tengu, Sept 2011) — no REDU-specific archive exists.
Card effect (current official text)If this card is in your hand or Graveyard when a face-up Beast-Type monster you control is destroyed and sent to the Graveyard (except during the Damage Step): You can pay 1000 Life Points; Special Summon this card.
Rulings
- You can only activate 1 Trigger Effect in your hand per chain. (You can't activate the ① effect of this card more that once per chain, even if you have multiple copies in your hand/GY).
- This card's effect cannot be activated in the Damage Step, so it cannot be activated when a Beast is destroyed by battle.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the REDU forum — sourced change requests get reviewed.