Right so came an adder out of a little heathbush, and it stung a knight in the foot. … and anon he drew his sword to slay the adder, and thought none other harm. and when the host on both parties saw that sword drawn, then they blew beams, trumpets, horns, and shouted grimly. … and king arthur took his horse and said, “alas, this unhappy day! ” and so rode to his party, and sir mordred in like wise. what is the main idea of this passage from morte d’arthur by sir thomas malory? king arthur and sir mordred are expressing their distrust of each other. sir mordred fatally wounds king arthur. king arthur attempts to slay, or kill, sir mordred. a knight kills a snake with his sword.