Baligant might just win the gold star for being the most mysterious fellow in the entire poem.
Broadly, he serves as a narrative foil to Charlemagne: Charlemagne is ruler of the Frankish empire and feudal lord to the knights who serve him and the rulers who rule the kingdoms included in his empire. Baligant, on the other hand, is the non-Christian version of Charlemagne: although his home is in Babylon, he rules over the vast Muslim/non-Christian empire that stretches from the Middle East to Spain. Marsile is ruling Saragossa as his vassal.
But what makes Baligant strange is his sense of timing. Marsile informs him that the Franks are kicking up trouble in Spain during the very first year of Charlemagne's seven-year war. But even if Baligant did get the telegram, he sure is slow in getting it together.
Not until Marsile hobbles home with a severed hand post-Roncevaux does Baligant finally show up. And that's not because he received an urgent update either. When his messengers tell him about Marsile and his recent calamities, he is astonished and angry. So the question remains: what roused the Emir out of Babylon? Did he finally wake up to the fact that Charlemagne had conquered most of his Spanish fiefs? Did he feel something in his bones? Does he have visions like Charlemagne? The poet, who admittedly is pretty pro-Charlemagne, never tells us.
Once roused though, the Emir is raring to go. He arrives in Spain anxious to kill Franks and seeing Marsile's defeat only makes him more anxious. This is a man with war and revenge on the mind, yet in the middle of his epic battle with Charlemagne, he also offers the most pragmatic take on the war:
Think it over, Charles,
You'd be well advised to beg my forgiveness!
You have slain my son, of that I am certain,
You very unjustly challenge my right to this country. (260.3589-92)
Where the Franks are motivated by ideas of good v. evil (they are good, of course—did we even need to say that?), the Emir actually has real, moral, and political reasons for fighting Charlemagne.
First, Charlemagne just killed the Emir's son, which makes them even in the revenge department: the Saracens killed Roland, the Franks killed Malprimes. But think about this. Marsile's army killed Roland but Charlemagne is taking revenge on the Emir, not on Marsile at all. Does that make sense?
Well, you could argue that since Baligant and Marsile are allies, it is semi-reasonable, but isn't it a lot less reasonable than what the Emir is doing? Charlemagne's men killed his son, so now he wants to kill those men. How's that for direct, accurately targeted revenge? Second, the Emir claims that it's unjust for Charlemagne to even be in Spain because he (Baligant) owns this land. How would Charlemagne feel if Baligant invaded France? Pretty not good.
So even though the Emir looks like he's caught up in the same cycle of hate and revenge, he actually offers more sensible and well-thought-out reasons for war than anyone. Maybe he and Oliver should have been friends.