Rexorian

The Rexorians are a blue energy based lifeform from the planet Rexor IV, they feel no positive emotions like love, caring and devotion, only negative ones like hate and violence (though in one seen case this may not be true and therefore may be more compassionate than believed ), they are aggressive towards humans killing a number of them as soon as there space craft landed on there home world, they have the ability to metamorph, join with another living organism and inherit their DNA and memories making them very hard to spot.