// Hideaway (This land enters the battlefield tapped. When it does, look at the top four cards of your library, exile one face down, then put the rest on the bottom of your library.)
this.addAbility(new HideawayAbility(this));
// {tap}: Add {W} to your mana pool.
this.addAbility(new WhiteManaAbility());
// {W}, {tap}: You may play the exiled card without paying its mana cost if you attacked with three or more creatures this turn.
Ability ability = new ActivateIfConditionActivatedAbility(
Zone.BATTLEFIELD, new HideawayPlayEffect(), new ManaCostsImpl("{W}"), WindbriskHeightsAttackersCondition.getInstance());
ability.addCost(new TapSourceCost());
this.addAbility(ability);
this.addWatcher(new PlayerAttackedWatcher());
}