This humanoid hybrid was engineered by a great Octopire countess to serve as powerful watchmen over her human livestock. Unfortunately, combining the intelligence and cruelty of both hominid and delfinid resulted in a breed of cruel, perverse abominations with dangerously limited attention spans. The Dolfuries quickly proved the greatest danger to their own wards, submitting to dark temptations even their vampiric creator found unacceptably abusive. As the grotesque incidents grew more frequent and the transparent excuses more absurd, their mistress took increasingly extreme disciplinary measures which only seemed to excite the twisted mutants even further. When at last she attempted to destroy them, a single female narrowly escaped the Octopire's abyssal palace with developing offspring, and the monstrosities have thrived for centuries since.
Though mentally and biologically unstable, these half-dolphin sadists are as tenacious as they are destructive, defiling cetaceans and humanoids alike with their deadly parasitoid reproductive habits and easily adapting to extremes of temperature and pollution. They are popularly regarded as one of the only truly "evil" monsters ever created, and many attempts have been made to annihilate them.
Besides its incredible strength, a Dolfury's sonic tittering can cause intolerable pain and even tissue damage in complex beings. Dolfury are regarded in poor taste as minions, but heavy psychosurgery and behavioral drugs can moderately suppress nearly half of their depraved urges.
So really, no different from an actual dolphin, it just has legs.