def ELF_FROM_GRAVEYARD = new MagicCardFilterImpl() {
    public boolean accept(final MagicGame game,final MagicPlayer player,final MagicCard target) {
        return target.hasSubType(MagicSubType.Elf);
    }
    public boolean acceptType(final MagicTargetType targetType) {
        return targetType == MagicTargetType.Graveyard;
    }
};

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

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

        @Override
        public MagicEvent getPermanentEvent(final MagicPermanent source, final MagicPayedCost payedCost) {
            return new MagicEvent(
                source,
                this,
                "PN gains 1 life for each Elf card in his or her graveyard."
            );
        }

        @Override
        public void executeEvent(final MagicGame game, final MagicEvent event) {
            final MagicPlayer player = event.getPlayer();
            final int amount = game.filterCards(player, ELF_FROM_GRAVEYARD).size();
            game.doAction(new MagicChangeLifeAction(player,amount));
        }
    }
]