// Whenever you gain life, put a +1/+1 counter on Wall of Limbs.
this.addAbility(new WallOfLimbsTriggeredAbility());
// {5}{B}{B}, Sacrifice Wall of Limbs: Target player loses X life, where X is Wall of Limbs's power.
Effect effect = new LoseLifeTargetEffect(new SourcePermanentPowerCount());
effect.setText("Target player loses X life, where X is {this}'s power.");
Ability ability = new SimpleActivatedAbility(Zone.BATTLEFIELD, effect, new ManaCostsImpl("{5}{B}{B}"));
ability.addCost(new SacrificeSourceCost());
ability.addTarget(new TargetPlayer());
this.addAbility(ability);
}