REDU format ruling
Convulsion of Nature

Nearest-era rulings (Tengu, Sept 2011) — no REDU-specific archive exists.
Card effect (current official text)As long as this card remains face-up on the field, both players must turn their respective Decks upside down and proceed with the current Duel.
Rulings
- When this card’s effect is active, both Decks are flipped upside down, and now the face of the top card of the Deck is showing.
- If a card effect requires a player to shuffle their Deck, it is shuffled and cut face-down so the cards are not seen, and then placed face-up in the Deck Zone.
- If a Parasite Paracide is face-up in your Deck before this card is activated, it will become face-down once this card is active. Its effect will still activate when it is drawn.
- If 2 copies of Convulsion of Nature are active, the Decks are still upside-down (they do not revert to normal).
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the REDU forum — sourced change requests get reviewed.