REDU format ruling
Catoblepas and the Witch of Fate

Nearest-era rulings (Tengu, Sept 2011) — no REDU-specific archive exists.
Card effect (current official text)When your opponent Special Summons a monster(s), you can remove from play 1 monster with ? ATK from your Graveyard to destroy that Special Summoned monster(s).
Rulings
- You cannot activate this effect during the Damage Step.
- Removing from play 1 monster with ? is a cost.
- This effect does not target.
- If multiple monsters are Special Summoned at the same time, including Catoblepas and the Witch of Fate, you can activate its effect to destroy all your opponent's monsters that were Special Summoned at the same time.
- If you activate The Shallow Grave while you control Catoblepas and the Witch of Fate you can activate its effect to destroy the monster your opponent Special Summons.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the REDU forum — sourced change requests get reviewed.