Aslan, the lion deity of The Chronicles of Narnia, shows his importance by having A as the first letter of his name. In the English language, it’s the first letter of the alphabet. One language theory posits that modern humans, when they read written characters, use the same parts of the brain once used for analyzing landscape features. If true, then A is a mountain, not only the foremost character, but the most visually arresting and important. C. S. Lewis most likely modeled the name Aslan on Arslan, the Persian word for lion, wisely dropping the R because of its connotations to arse (British slang for buttocks.)
That there are two As is Aslan makes him doubly impressive.
In fantasy, A names are also equated with character importance much of the time, from Atreides to Ael (ninja-like tribesman from The Wheel of Time series) to Orson Scott Card’s hero Alvin Maker.
Here’s some randomgenned character names beginning with A.
Character names beginning with A