Mordred hates his father and his mother, so starts a rebellion seeking to impose a constitution and democracy.
The first insight is when he's dragged into court forcibly by Sir Kay and forced to be acknowledged by a concerned Arthur.
The queen's pissed and the PC's have to talk her down from having Lancelot end Arthur for his infidelity.
Lancelot and Kay impose a quest upon the PCs to "educate" Mordred in the arts of Chivalry...
Squire Mordred the Absent causes no shortage of problems for the party; repeat several times.
Arthur acknolwedges Mordred as heir; both Mordred and Guinevere go absent.
Mordred reveals Lancelot's lust for Guin... Publicly.
Cue PC's trying to either silence Mordred or stop Lance from shaming them by killing Mordred.
Guin goes missing again, PC's tasked to find her.
Guin comes back with Mordred, and has him baptized... sunday mass watches as he dissolves, being nought but a glamour...
Real Mordred is hiding out with Merlin, PC's have to talk him into parlay with his father.
Dragons Everywhere- The PCs are from a generically east Asian inspired land. There's metallic dragons everywhere, they're semi divine, part of the heavenly bureaucracy, yadda yadda yadda. That's just a backdrop for the invasion by a neighboring country that's the same sort of thing with the notable exception that their dragons have been swapped out for western/chromatic dragons