Jamieson, Fausset and Brown on Revelation 8:11

11. The symbolizers interpret the star fallen from heaven as a chief minister (Arius, according to Bullinger, Bengel, and others; or some future false teacher, if, as is more likely, the event be still future) falling from his high place in the Church, and instead of shining with heavenly light as a star, becoming a torch lit with earthly fire and smouldering with smoke. And "wormwood," though medicinal in some cases, if used as ordinary water would not only be disagreeable to the taste, but also fatal to life: so "heretical wormwood changes the sweet Siloas of Scripture into deadly Marahs" [Wordsworth]. Contrast the converse change of bitter Marah water into sweet, Ex 15:23. Alford gives as an illustration in a physical point of view, the conversion of water into firewater or ardent spirits, which may yet go on to destroy even as many as a third of the ungodly in the latter days.