The Dominatrix (plural: Dominatrices, species name: tyranicus praepotens) is one of the species of Tyranids. They are Synapse Creatures and a major part of the collective Hive Mind, and thus high in the Tyranid hierarchy.
It is a gargantuan composite creature of nightmarish proportions, equipped with ripping claws and fangs, and a stunning profusion of symbiotic weaponry. Dominatrices are the brood queens of the Tyranid hordes , their children spawning into all the different Tyranid classes. Inside her are all the gene sequences of the galaxy's most lethal creatures, ready to be spliced and twisted by the Hive Mind.
Because of the importance of a Dominatrix, which is also the most powerful link to the Hive Mind a horde has, they are strategic targets of the highest priority. Destroying a Dominatrix can decide whether a planet falls to the Great Devourer, or is saved.