magarena/release/Magarena/scripts/Sunken_City.groovy

[
    new MagicAtUpkeepTrigger() {
        @Override
        public MagicEvent executeTrigger(final MagicGame game,final MagicPermanent permanent,final MagicPlayer upkeepPlayer) {
            return permanent.isController(upkeepPlayer) ?
                new MagicEvent(
                    permanent,
                    new MagicMayChoice(
                        new MagicPayManaCostChoice(MagicManaCost.create("{U}{U}"))
                    ),
                    this,
                    "PN may\$ pay {U}{U}\$. If you don't, sacrifice SN."
                ) :
                MagicEvent.NONE;
        }

        @Override
        public void executeEvent(final MagicGame game, final MagicEvent event) {
            if (event.isNo()) {
                game.doAction(new MagicSacrificeAction(event.getPermanent()));
            }
        }
    }
]