REDU format ruling
Magic Cylinder

Nearest-era rulings (Tengu, Sept 2011) — no REDU-specific archive exists.
Card effect (current official text)When an opponent's monster declares an attack: Target the attacking monster; negate the attack, and if you do, inflict damage to your opponent equal to its ATK.
Rulings
- If that monster isn't face-up when this resolves, no damage is dealt.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the REDU forum — sourced change requests get reviewed.