Laevateinn, the Demon Sword
Race and Trait
Your J-ruler gains [Swiftness].
[rest]: Until end of turn, if your J-ruler would deal damage, it deals that much +200 instead. As long as your J-ruler is "Melgis, the One Charmed by the Demon Sword", it gains [Imperishable] until end of turn and you may pay  less to play its God's Art abilities this turn.
Banish a resonator: Recover this card.
Discard another card named "Laevateinn, the Demon Sword": Produce [R].
Banish this card: Your J-ruler gains [Imperishable] until end of turn.
The sword destined to those who crave power.
- If Zero, six sage of light uses her active ability on a J-ruler which has [Swiftness] provided by Laevatinn, the continuous ability of Laevateinn restores [Swiftness] right when zero's effect is resolved, is that so? If yes: If a J-ruler has declared an attack because of [Swiftness] provided by laevatin, Zero, six sage of light could use its active ability and stop the attack then [Swiftness] is restored by laevateinn?
Due to the nature if time stamps, If 《Laevateinn, the Demon Sword》 was played and 《Zero, Six Sage of Light》 used her activate ability to rob that J-ruler of Swiftness, it would not gain it back immediately. the only way to gain Swiftness that turn after Zero's effect had resolved is to play another Laevateinn or similar card to give that J-ruler swiftness.If a card with Swiftness declares an attack and you use Zero's ability to remove Swiftness for the turn, it does not stop the attack. The attack has already been declared. Swiftness only enables the declaring of the attack on the turn the J/resonator entered the field, which has already been done by the time you're playing Zero's ability in this example. You'd have to remove Swiftness before declaration of attack. Zero's ability does not cancel an attack.