At the far end of the lists (в дальнем конце ристалища), there were already so many knights on horses (уже находилось так много рыцарей верхом /на конях/) that the audience could only see a sea of shining helmets (что зрители могли видеть только море сверкающих шлемов;
already [ɔ:l'redɪ], shining ['ʃaɪnɪŋ], helmet ['helmɪt]
At the far end of the lists, there were already so many knights on horses that the audience could only see a sea of shining helmets. With the eyes of the crowd on them, the first five knights rode forward to the tents of the five challengers.
Each knight touched the shield of one of the challengers (каждый рыцарь коснулся щита одного из зачинщиков) with the back end of his lance (тупым: «задним» концом своего копья) and rode back to the end of the lists (и поскакал назад, к /другому/ концу ристалища). The challengers, led by the Templar (зачинщики /турнира/, ведомые рыцарем храма = под предводительством тамплиера;
knight [naɪt], mounted ['maʋntɪd], opposite ['ɔpǝzɪt]
Each knight touched the shield of one of the challengers with the back end of his lance and rode back to the end of the lists. The challengers, led by the Templar, then mounted their horses and rode to the opposite end of the lists.
At the sound of the herald's trumpet (при звуках трубы герольда) the two sides galloped towards each other (противники: «две стороны» поскакали галопом =
trumpet ['trʌmpɪt], gallop ['ɡælǝp], towards [tǝ'wɔ:dz]
At the sound of the herald's trumpet the two sides galloped towards each other. The crowd heard the lances break and saw that the challengers had knocked four of the knights off their horses.