Dark Ruler No More

Per-phrase breakdown

• Negate the effects of face-up monsters your opponent currently controls, until the end of this turn, also for the rest of this turn after this card resolves, your opponent takes no damage. (Effect)
• Neither player can activate monster effects in response to this card's activation. (Condition)

Judge-facing facts

• This card does not target.
• The text preventing players from activating monster effects in response to this card's activation is not an effect.
• Negates the effects of all face-up monsters in the opponent's Monster Zone at resolution.
• If a monster negated by this card activates an effect on the field by leaving the Monster Zone as cost (e.g., Tributing or banishing itself), that effect is still negated.
• If a monster negated by this card activates an effect in the Graveyard, that effect is not negated.
• If a monster negated by this card ceases to be face-up in the Monster Zone, the negation stops applying to it.
• The effect "your opponent takes no damage" applies as long as this card's activation and effect are not negated, even if no monster effects were successfully negated.

Card-specific notes from database

• (Konami neuron) If a monster's effects are already negated by "Skill Drain" when this card resolves, this card's negation is not applied to that monster; if "Skill Drain" later stops applying, that monster's effects will no longer be negated.
• (YGOResources) You can activate effects that inflict damage while this card's effect is applying, but because no damage is inflicted, you cannot apply any subsequent parts of the effect that depend on inflicting damage (e.g., "then you can Special Summon").
• (YGOResources) If multiple effects change damage calculation, damage redirection (e.g., "Nightmare Pain") is applied before damage reduction to 0 (e.g., "Dark Ruler No More"). The redirected damage becomes 0.