There are multiple synonyms for "twilight merged into darkness." Some possible options include "dusk turned to night," "sunset gave way to blackness," "daylight faded to obscurity," "evening blended with shadows," and "the last light flickered and extinguished." Each of these phrases conjures a sense of the transition between light and dark, and suggests a gradual fading away of brightness and clarity. Whether used in literature or everyday language, these synonyms offer a range of ways to describe a moment of fading light and the deepening onset of night.