"Trystanbull" is a tag that seems to combine two elements: "Triton," which is likely referring to the mythical Greek god Triton, and "Bull." The combination of these two elements suggests a theme involving a powerful or dominant figure (the bull) with a touch of fantasy or mythology (the reference to Triton). This tag could be used for a porn video that features a strong, muscular, or dominant male, possibly with an aquatic or sea-related fetish, or a scene that involves roleplaying with mythological themes.