REDU format ruling
The Agent of Judgment - Saturn

Nearest-era rulings (Tengu, Sept 2011) — no REDU-specific archive exists.
Card effect (current official text)While your Life Points are higher than your opponent's, you can Tribute this card to inflict damage to your opponent equal to the difference. If you do not control a face-up "The Sanctuary in the Sky", this effect is not applied. You cannot conduct your Battle Phase the turn you activate this effect.
Rulings
- Tributing The Agent of Judgment - Saturn is a cost.
- You cannot activate The Agent of Judgment - Saturn's effect during Main Phase 2. You CAN activate The Agent of Judgment - Saturn's effect during Main Phase 1 even if you have to skip your Battle Phase because of a card effect.
- You can activate multiple The Agent of Judgment - Saturns' effects in the same turn.
- You can chain Barrel Behind the Door to The Agent of Judgment - Saturn's effect.
- If The Sanctuary in the Sky is not on the field, you can Tribute The Agent of Judgment - Saturn and activate the effect, but the effect is not applied and disappears.
- If an effect is chained to The Agent of Judgment - Saturn's effect that would increase your opponent's Life Points, so that your opponent's Life Points are higher than yours when its effect resolves, then The Agent of Judgment - Saturn's effect disappears because your Life Points need to be higher than your opponent's when the effect resolves.
- Damage is calculated and inflicted when the effect resolves, so calculate the exact damage when resolving the effect, including any chained effects that altered the Life Points since activation; if the Life Points have changed since activation, the damage inflicted changes accordingly.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the REDU forum — sourced change requests get reviewed.