magarena/release/Magarena/scripts/Kor_Duelist.groovy

[
    new MagicStatic(MagicLayer.Ability) {
        @Override
        public void modAbilityFlags(
                final MagicPermanent source,
                final MagicPermanent permanent,
                final Set<MagicAbility> flags) {
            if (permanent.isEquipped()) {
                flags.add(MagicAbility.DoubleStrike);
            }
        }
    }
]