this.supertype.add("Snow");
// Coldsteel Heart enters the battlefield tapped.
this.addAbility(new EntersBattlefieldTappedAbility());
// As Coldsteel Heart enters the battlefield, choose a color.
this.addAbility(new EntersBattlefieldAbility(new ChooseColorEffect(Outcome.Neutral)));
// {tap}: Add one mana of the chosen color to your mana pool.
this.addAbility(new SimpleManaAbility(Zone.BATTLEFIELD, new ColdsteelHeartManaEffect(), new TapSourceCost()));
}