Kieron Gillen 
Once & Future #20 

ARTHUR VS. ARTHUR!Knowing that Grail Castle may be their best chance at survival, Bridgette, Duncan, and Rose hunker down and prepare for the worst.Elsewhere, the resurrected King Arthur challenges an arriving usurper to his rightful throne, another King Arthur, and raises an army of the undead to do it. But the new Arthur has the greatest knight of all on his side – Lancelot!