Another round of weekly creature design fun at conceptart.org, for those who cares, could go check it out at

[LINK: Conceptart.org Heart Harvester]

No one knows where they came from, no one have seen their nesting ground. The Hell Harvesters travels at night and can hear the heart beats of living creatures from far away, as they track down their prey, they dive from the air and accurately chisel the front of their head into the prey's chest and launches their spike-like feet and tail to penetrate into the chest around the area of the heart. Just as quickly, the harvester push its body back with its powerful tail and wing, with the help of the saw-like hooks at the back of the feet and tail, it breaks the ribcage and rips the heart out. The inner-lining of the tail and feet contain soft short tentacles to hold the heart firmly in place while not destroying it, the harvested then fly back to the nesting ground with the harvested heart.
For some strange reason, the Harvester actaully does not eat the heart, but instead later returns to feed on the prey's corpse. No one really knows why, perhaps it is to mark their territory to fear off any intruders. Some rumors that they're creatures from hell, minions of death and bringing and end to the world...