How to use

ExileSourceUnlessPaysEffect

in

mage.abilities.effects.common

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

public DemonlordOfAshmouth(UUID ownerId, CardSetInfo setInfo) {
  super(ownerId,setInfo,new CardType[]{CardType.CREATURE},"{2}{B}{B}");
  this.subtype.add(SubType.DEMON);
  this.power = new MageInt(5);
  this.toughness = new MageInt(4);
  this.addAbility(FlyingAbility.getInstance());
  // When Demonlord of Ashmouth enters the battlefield, exile it unless you sacrifice another creature.
  this.addAbility(new EntersBattlefieldTriggeredAbility(new ExileSourceUnlessPaysEffect(new SacrificeTargetCost(new TargetControlledPermanent(filter)))));
  this.addAbility(new UndyingAbility());
}

public BodySnatcher(UUID ownerId, CardSetInfo setInfo) {
  super(ownerId, setInfo, new CardType[]{CardType.CREATURE}, "{2}{B}{B}");
  this.subtype.add(SubType.MINION);
  this.power = new MageInt(2);
  this.toughness = new MageInt(2);
  // When Body Snatcher enters the battlefield, exile it unless you discard a creature card.
  this.addAbility(new EntersBattlefieldTriggeredAbility(new ExileSourceUnlessPaysEffect(new DiscardTargetCost(new TargetCardInHand(new FilterCreatureCard("a creature card"))))));
  // When Body Snatcher dies, exile Body Snatcher and return target creature card from your graveyard to the battlefield.
  Effect effect = new ReturnFromGraveyardToBattlefieldTargetEffect();
  effect.setText("and return target creature card from your graveyard to the battlefield");
  Ability ability = new DiesTriggeredAbility(new ExileSourceEffect(), false);
  ability.addEffect(effect);
  ability.addTarget(new TargetCardInYourGraveyard(StaticFilters.FILTER_CARD_CREATURE_YOUR_GRAVEYARD));
  this.addAbility(ability);
}