The former Law & Order: SVU star plays Roman, guardian of the Vampire Authority, in the HBO drama's fifth season.
"He's the political and spiritual leader, whether he's self-appointed or not, we never get to," Meloni explained to TV Guide. "[His position on enemies is] kill them all. Reasoning can only go so far, then you've got to resort to the stake."
Meloni hinted that Roman could clash with rogue vampire Russell Edgington (Denis O'Hare).
"He truly does have incredible strength as a vampire because of his age, so I think he's a natural enemy," he explained. "On top of it, I think he's unstable. There's nothing worse than an old, psychopathic vampire."
The 51-year-old actor added that he is relishing the opportunity to explore a character so different from his SVU role of cop Elliot Stabler.