REDU format ruling
Criosphinx

Nearest-era rulings (Tengu, Sept 2011) — no REDU-specific archive exists.
Card effect (current official text)When a monster is returned from the field to the owner's hand, the owner of the returned monster selects and sends 1 card in their hand to the Graveyard.
Rulings
- The effect of "Criosphinx" is a Trigger Effect, and can be chained to. You can activate "Divine Wrath" against it. If a monster is returned to the hand in the middle of a chain, the effect of "Criosphinx" activates as a new chain after the previous chain has finished resolving.
- If multiple copies of "Criosphinx" are in play and a monster is returned to the hand, all copies will activate. It forms a chain, with the turn player’s "Criosphinx" as chain link 1.
- If multiple monsters are sent to the hand simultaneously (such as with "Guardian Sphinx"), the effect of "Criosphinx" only activates once, so only 1 card is sent to the GY.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the REDU forum — sourced change requests get reviewed.