REDU format ruling
Belial - Marquis of Darkness

Nearest-era rulings (Tengu, Sept 2011) — no REDU-specific archive exists.
Card effect (current official text)Your opponent cannot target any face-up monster you control, except "Belial - Marquis of Darkness", for an attack, or with Spell/Trap effects.
Rulings
(1) Your opponent cannot select any monster you control, except Belial - Marquis of Darkness, as an attack target, or as a target of a Spell or Trap Card.
- The (1) Continuous Effect applies so long as Belial - Marquis of Darkness is face-up on the field.
- If a Spell / Trap Card targets 1 monster you control and you chain Call of the Haunted to Special Summon Belial - Marquis of Darkness, the effect is still resolved as normal.
- Monsters in your GY can still be targeted by your opponent's Spell / Trap Cards.
- This effect does not apply to face-down monsters you control [REF needed, errata'd in 2011].
- While the (1) Continuous Effect applies, your opponent can:
- use Spell / Trap Cards which do not target (ex: Bottomless Trap Hole, Smashing Ground);
- target your other monsters with monster effects (ex: Caius the Shadow Monarch);
- target your face-down Defense Position monsters with Spell / Trap Cards & Effects [REF needed, errata'd in 2011];
- attack your face-down Defense Position monsters [REF needed, errata'd in 2011].
- If you control Evil HERO Malicious Fiend & Belial - Marquis of Darkness, and their effects are active, your opponent's monsters are changed to Attack Position and must attack Evil HERO Malicious Fiend.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the REDU forum — sourced change requests get reviewed.