REDU format ruling
Pandemonium

Nearest-era rulings (Tengu, Sept 2011) — no REDU-specific archive exists.
Card effect (current official text)Neither player has to pay Life Points during the Standby Phase for "Archfiend" monsters. Each time a player's "Archfiend" monster(s) is destroyed and sent to the Graveyard, except by battle, that player can add 1 "Archfiend" monster from their Deck to their hand that is a lower Level than the destroyed card.
Rulings
- You can't use Pandemonium to add a Fusion Monster Archfiend or Synchro Monster Archfiend from the Extra Deck to your hand, like Fiend Skull Dragon or Red Dragon Archfiend.
- If multiple Archfiends are destroyed at the same time by Raigeki, you can only add 1 Archfiend from your Deck to your hand with Pandemonium.
- When your Archfiends controlled by your opponent are sent to your GY, you can add an Archfiend from your Deck to your hand with Pandemonium.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the REDU forum — sourced change requests get reviewed.