Ganelon Timeline and Summary

First this sneaky guy advises Charlemagne that Blancandrin is telling the truth about Marsile's intentions.
Then, he reacts with anger when Roland nominates him to be the messenger and promises revenge.
He plots with Blancandrin to destroy Roland.
Then, he persuades Marsile that a ruse of fake conversion, fake offers of vassalage, and actual destruction. of Roland's rearguard is the way to break Charlemagne. Boo. Hiss.
He rides back to Charlemagne with gifts and (supposedly) good news.
Jerk nominates Roland to lead the rearguard.
But he pooh-poohs Charlemagne's alarm when they hear the oliphant, claiming it's no battle, only Roland's arrogance.
He's turned over to Charlemagne's kitchen servants once his treachery is exposed.
Then he declares on trial that he hates Roland for cheating him out of the big bucks.
Finally—finally—he's sentenced to death by drawing and quartering. Good riddance.