The problem right now is the horses. Actually, there are uncountable problems, but the problem that Tristan has the tool to deal with is the horses.

He lets loose arrows as hard and as fast as he can. The act of drawing the sword from its sheath must be the decisive killing blow. Four arrows fly at full strength, three horses necks are shredded beyond utility - two in Pellinore's, and one each in the immediate flanks of her V. Now they are out of formation, and their charge will not hit as one crashing wave, but in two staggered blows. 

The knights at the edges have to steer their horses out of the way of the crashing, foaming heaps of their allies. Pellinore surfs her own mount down to the ground and dismounts it easily. Unharmed, but unable to lead the rest of her knights in their charge against the two living mountains and champion jousters between them and stopping Tristan. 

The devestation of the earth itself tearing itself asunder surrounds them.

Tristan wishes he had the satisfaction of being exhausted, after such a sprint, but his arms just feel the swell of blood rush into them, he feels stronger and faster than he started. May Robena and Sandsfern find this sufficient gratitude for gifting him a chance to rest. He nocks another arrow. 

"The land is sick!" He speaks like a bard to a deep crowd - not shouting, but projecting his voice from deep in his stomach, steady and unwavering. He never liked how soldiers shouted. Never liked the weak vibrato of startlement and anger. "You can see it. I have ridden with you, and you know me to be good and to be true. Pellinore is cause and symptom! I hope you will join us in its cure, but will accept that you not stand against us! You will run out of throats before I run out of arrows."  

[Leap into action: 5, 5 +0 = 10 
I inflict harm
I startle or scatter]