Mist Bird Clausolas

Regarding the effect: "Once per turn, you can target 1 face-up monster your opponent controls; its ATK becomes 0, and its effects are negated until the end of this turn."

This is an Ignition Effect that can be activated in the Monster Zone.

This effect targets 1 face-up monster in your opponent's Monster Zone.

If the monster's ATK is not 0, you can target a Normal Monster or a monster whose effects are already negated to activate this effect.

You cannot target a monster with 0 ATK to activate this effect.

If a monster to which this effect was applied is changed to face-down Defense Position, the application of this effect ends.

If a monster to which this effect was applied leaves the Monster Zone as a cost to activate its own effect, or leaves the Monster Zone due to the cost or resolution of an effect activated in a chain, its effects are negated, so that resolution does not occur.