// Trample
this.addAbility(TrampleAbility.getInstance());
// Altar Golem's power and toughness are each equal to the number of creatures on the battlefield.
DynamicValue amount = new PermanentsOnBattlefieldCount(new FilterCreaturePermanent("creatures in play"));
this.addAbility(new SimpleStaticAbility(Zone.BATTLEFIELD, new SetPowerToughnessSourceEffect(amount, Duration.WhileOnBattlefield)));
// Altar Golem doesn't untap during your untap step.
this.addAbility(new SimpleStaticAbility(Zone.BATTLEFIELD, new SkipUntapSourceEffect()));
// Tap five untapped creatures you control: Untap Altar Golem.