Christian is a headstrong young baron who just arrived from Gascony and means to join the Guards. Christian’s defining features are his good looks, and the fact that he is totally unable to verbalize his thoughts and feelings.
Because of his inability to speak articulately, Christian’s love for Roxane is made possible only with Cyrano’s literary help. He shows some spirit in wanting to win Roxane for himself – without Cyrano’s aid – but for the most part, he comes across as a dense and passive character, at least at first. Later, we see that Christian may not actually be all that dumb.
Intellect aside, Christian shows a surprising degree of compassion. He sacrifices a night with Roxane to warn his friend Lignière of a death threat. This not only entails leaving Roxane, but roaming the streets of Paris to find all the taverns, physically going in and writing a letter of warning for Lignière, and possibly putting himself in mortal danger. It is quite a sacrifice for a young lovelorn man. Also, when Roxane shows up in her carriage at the battlefield of Arras, Christian is one of the men who urges her to leave – for the sake of her safety. Even though he misses her terribly, Christian willingly orders her away when he knows he will never see her again. This shows a certain emotional depth to him that we readers had not suspected before. Even Roxane, upon Christian’s death, says "[he had] a heart deeper than we knew."
Speaking of, Christian’s name may have religious overtones. He is a simple man – compassionate, brave, and ultimately good. He dies as something of a martyr – so that Roxane may live and so that she may love the man who has always loved her. His final letter, which Roxane wears over her heart, is referred to as a "holy reliquary." His goodness is sometimes associated with light imagery, in sharp contrast to Cyrano, who is often hidden in shadows.
So back to this part about Christian being smarter than he looks. Crazy, you say? Consider this: every time he speaks to Cyrano about winning Roxane, he questions why Cyrano helps him. He does not just accept Cyrano’s help blindly; he wants to know Cyrano’s motive. True, he’s not exactly Sherlock Holmes in his sleuthing, but he does eventually catch on. And check out his lines in Act II when he cleverly insults Cyrano’s nose over and over while Cyrano is telling the story of the previous night. Sure, the fact that he’s insulting him is stupid as hell, but the way in which he does it is almost as witty as Cyrano’s list of insults in Act I. It could be, then, that Christian isn’t too stupid to serenade Roxane – he’s just too nervous. In that case, both Christian and Cyrano need each other’s help for the same reason: lack of confidence. Look, they’re even more similar than we thought.