How to insert an arrow symbol in legend?

Hi, I want to insert the arrow symbol in legend, but the arrow is not one of the plotted objects. I have tried to use the marker, but the result is not that good. I attach both images, the result of this script and the "wanted" result. Thank you.

[X,Y,Z] = peaks;
figure
[~,L3]= contour(X,Y,Z,10,'r');
hold on
q = 0;
L1= plot (xlim,[1 1]*q,'LineWidth',2);
tes=L1.Color
L1.Color='blue'
a=0
L2= plot ([1 1]*a,ylim,':k','LineWidth',2);
L4 = plot(NaN,NaN,'->b');
lgd=legend([L2 L3 L4],{'threshold','contour','arrow'},...
 'location','northeast')
lgd.FontSize = 15;

Answer 1

[KSSV]

[X,Y,Z] = peaks;
figure
[~,L3]= contour(X,Y,Z,10,'r');
hold on
q = 0;
L1= plot (xlim,[1 1]*q,'LineWidth',2);
tes=L1.Color
L1.Color='blue'
a=0
L2= plot ([1 1]*a,ylim,':k','LineWidth',2);
L4 = quiver(10,10,1,0,'b');
lgd=legend([L2 L3 L4],{'threshold','contour','arrow'},...
 'location','northeast')
lgd.FontSize = 15;
axis([-3 3 -3 3])

[Amra Rajuli]

thank you