Tetrax Shard is a Petrosapien – aka Ben's Diamondhead – a diamond-hard alien with the ability to shoot crystal shards from his body. He began as a bounty hunter whose selfishness inadvertently led to the destruction of his home planet Petropia. Since then, he has become a sort of mentor for Ben, showing up at crucial times to help the young Omnitrix-bearer train to use his powers with greater skill and strategy.