How to use

mage.abilities.effects.common.continuous.BecomesEnchantmentSourceEffect

constructor

@Override
public BecomesEnchantmentSourceEffect copy() {
  return new BecomesEnchantmentSourceEffect(this);
}

public OpalAcrolith(UUID ownerId, CardSetInfo setInfo) {
  super(ownerId, setInfo, new CardType[]{CardType.ENCHANTMENT}, "{2}{W}");
  // Whenever an opponent casts a creature spell, if Opal Acrolith is an enchantment, Opal Acrolith becomes a 2/4 Soldier creature.
  TriggeredAbility ability = new SpellCastOpponentTriggeredAbility(new BecomesCreatureSourceEffect(new OpalAcrolithToken(), "", Duration.WhileOnBattlefield, true, false),
      filter, false);
  this.addAbility(new ConditionalInterveningIfTriggeredAbility(ability, new SourceMatchesFilterCondition(StaticFilters.FILTER_ENCHANTMENT_PERMANENT),
      "Whenever an opponent casts a creature spell, if Opal Acrolith is an enchantment, Opal Acrolith becomes a 2/4 Soldier creature."));
  // {0}: Opal Acrolith becomes an enchantment.
  this.addAbility(new SimpleActivatedAbility(Zone.BATTLEFIELD, new BecomesEnchantmentSourceEffect(), new ManaCostsImpl("{0}")));
}

public HiddenStag(UUID ownerId, CardSetInfo setInfo) {
  super(ownerId, setInfo, new CardType[]{CardType.ENCHANTMENT}, "{1}{G}");
  // Whenever an opponent plays a land, if Hidden Stag is an enchantment, Hidden Stag becomes a 3/2 Elk Beast creature.
  Effect effect = new BecomesCreatureSourceEffect(new ElkBeastToken(), "", Duration.WhileOnBattlefield, true, false);
  TriggeredAbility ability = new OpponentPlaysLandTriggeredAbility(Zone.BATTLEFIELD, effect, false);
  this.addAbility(new ConditionalInterveningIfTriggeredAbility(ability, new SourceMatchesFilterCondition(StaticFilters.FILTER_ENCHANTMENT_PERMANENT),
      "Whenever an opponent plays a land, if Hidden Stag is an enchantment, Hidden Stag becomes a 3/2 Elk Beast creature."));
  // Whenever you play a land, if Hidden Stag is a creature, Hidden Stag becomes an enchantment.
  Effect effect2 = new BecomesEnchantmentSourceEffect();
  TriggeredAbility ability2 = new ControllerPlaysLandTriggeredAbility(Zone.BATTLEFIELD, effect2, false);
  this.addAbility(new ConditionalInterveningIfTriggeredAbility(ability2, new SourceMatchesFilterCondition(StaticFilters.FILTER_PERMANENT_CREATURE),
      "Whenever you play a land, if Hidden Stag is a creature, Hidden Stag becomes an enchantment."));
}