An author shouldn’t really have to justify their decisions for a story in progress, but I know some people are going to ask so let’s cut right to the point.
I killed off Sir Tristan rather swiftly, and with what appeared to be a nearly lopsided battle. By the amount of damage he was still able to inflict with a severely diminished blessing and a disabled gift, he could be a serious menace if allowed to escape. The amount of servants taking him on at once also puts him at a disadvantage, yet he was still very capable of killing them all off without his blessing as evidenced by nearly destroying the Chaldean knights. So what happened to even the scales should have been very obvious.
The Count of Monte Cristo happened.
Sending Dantes was more or less a lucky decision by Gudao. The archers aren’t able to hit because of Sir Tristan’s combat abilities, which also make him very much impossible to dodge had Bedivere not landed his debilitating strike since his attack essentially travels at the speed of sound. But Dantes can move at the speed of thought, which is a very dangerous ability for any ranged opponent. He’s essentially the counter to Sir Tristan, who was only finally able to incapacitate him by predicting his movements and creating a localized shock wave.
About Sir Tristan’s design: The most I could ever find was that he uses vacuum based sonic attacks without much description, so pairing that with his bow being a musical instrument, I took a little creative liberty. By playing the instrument, it uses sound waves as the slicing blades, therefore giving his projectiles their invisible nature and swift speed; The blessing only amplified this power. Since it’s a sound wave, it still has to travel in a linear direction but can be redirected by being bounced off walls which is why he’s able to hit targets he can’t see.
Obviously this rescue went smoother than they anticipated, even if several servants receiving injuries: They killed a knight of the round, and that’s not going to go unnoticed in the least.