How to use

ExchangeLifeTargetEffect

in

mage.abilities.effects.common

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

public MirrorUniverse(UUID ownerId, CardSetInfo setInfo) {
  super(ownerId, setInfo, new CardType[]{CardType.ARTIFACT}, "{6}");
  // {tap}, Sacrifice Mirror Universe: Exchange life totals with target opponent. Activate this ability only during your upkeep.
  Ability ability = new ConditionalActivatedAbility(
      Zone.BATTLEFIELD,
      new ExchangeLifeTargetEffect(),
      new TapSourceCost(),
      new IsStepCondition(PhaseStep.UPKEEP, true),
      null);
  ability.addCost(new SacrificeSourceCost());
  ability.addTarget(new TargetOpponent());
  this.addAbility(ability);
}

public MagusOfTheMirror(UUID ownerId, CardSetInfo setInfo) {
  super(ownerId, setInfo, new CardType[]{CardType.CREATURE}, "{4}{B}{B}");
  this.subtype.add(SubType.HUMAN);
  this.subtype.add(SubType.WIZARD);
  this.power = new MageInt(4);
  this.toughness = new MageInt(2);
  // {tap}, Sacrifice Magus of the Mirror: Exchange life totals with target opponent. Activate this ability only during your upkeep.
  Ability ability = new ConditionalActivatedAbility(
      Zone.BATTLEFIELD,
      new ExchangeLifeTargetEffect(),
      new TapSourceCost(),
      new IsStepCondition(PhaseStep.UPKEEP),
      null);
  ability.addCost(new SacrificeSourceCost());
  ability.addTarget(new TargetOpponent());
  this.addAbility(ability);
}