magarena/release/Magarena/scripts/Lunar_Mystic.groovy

[
    new MagicWhenOtherSpellIsCastTrigger() {
        @Override
        public MagicEvent executeTrigger(final MagicGame game, final MagicPermanent permanent, final MagicCardOnStack spell) {
            return permanent.isFriend(spell) && spell.isSpell(MagicType.Instant) ?
                new MagicEvent(
                    permanent,
                    new MagicMayChoice(
                        new MagicPayManaCostChoice(MagicManaCost.create("{1}"))
                    ),
                    this,
                    "PN may\$ pay {1}\$. If you do, draw a card."
                ):
                MagicEvent.NONE;
        }

        @Override
        public void executeEvent(final MagicGame game, final MagicEvent event) {
            if (event.isYes()) {
                game.doAction(new MagicDrawAction(event.getPlayer()));
            }
        }
    }
]