magarena/release/Magarena/scripts/Assemble_the_Legion.groovy

[
    new MagicAtUpkeepTrigger() {
        @Override
        public MagicEvent executeTrigger(final MagicGame game,final MagicPermanent permanent,final MagicPlayer upkeepPlayer) {
            return permanent.isController(upkeepPlayer) ?
                new MagicEvent(
                    permanent,
                    this,
                    "PN puts a muster counter on SN. Then put a 1/1 red and white Soldier creature token with haste onto the battlefield for each muster counter on SN."
                ):
                MagicEvent.NONE;
        }
        @Override
        public void executeEvent(final MagicGame game, final MagicEvent event) {
            final MagicPermanent perm = event.getPermanent()
            game.doAction(new MagicChangeCountersAction(
                perm,
                MagicCounterType.Charge,
                1,
                true
            ));
            game.doAction(new MagicPlayTokensAction(
                event.getPlayer(),
                TokenCardDefinitions.get("1/1 red and white Soldier creature token with haste"), 
                perm.getCounters(MagicCounterType.Charge)
            ));
        }
    }
]