magarena/release/Magarena/scripts/Omnibian.groovy

def PT = new MagicStatic(MagicLayer.SetPT, MagicStatic.UntilEOT) {
    @Override
    public void modPowerToughness(final MagicPermanent source,final MagicPermanent permanent,final MagicPowerToughness pt) {
        pt.set(3,3);
    }
};

def ST = new MagicStatic(MagicLayer.Type, MagicStatic.UntilEOT) {
    @Override
    public void modSubTypeFlags(final MagicPermanent permanent,final Set<MagicSubType> flags) {
        flags.removeAll(MagicSubType.ALL_CREATURES);
        flags.add(MagicSubType.Frog);
    }
};

[
    new MagicPermanentActivation(
        new MagicActivationHints(MagicTiming.Removal),
        "Frog"
    ) {

        @Override
        public Iterable<MagicEvent> getCostEvent(final MagicPermanent source) {
            return [new MagicTapEvent(source)];
        }

        @Override
        public MagicEvent getPermanentEvent(final MagicPermanent source,final MagicPayedCost payedCost) {
            return new MagicEvent(
                source,
                MagicTargetChoice.TARGET_CREATURE,
                new MagicBecomeTargetPicker(3,3,false),
                this,
                "Target creature\$ becomes a 3/3 Frog until end of turn."
            );
        }

        @Override
        public void executeEvent(final MagicGame game, final MagicEvent event) {
            event.processTargetPermanent(game, {
                final MagicPermanent creature ->
                game.doAction(new MagicBecomesCreatureAction(creature,PT,ST));
            } as MagicPermanentAction);
        }
    }
]