Knight Thralls are essentially 'zombie' Templar Knights. They have a tattered, dull grey/blue appearance. They have blue glowing eyes and when shot, they emit blue 'clouds'. They wear helmets, armour on their arms and torso, long boots and hold shields.
Knight Thralls go for a kill first, think later approach. They will charge and hit Lara knocking her over. Unlike the Mayan, Tiger and Panther Thralls, the Knight Thrall can spit a harmful goo. The Shotgun is very effective against them being able to take one down in a few shots. Adrenaline Headshots can kill a Knight Thrall in one shot as can sticky grenades. Once a Viking Thrall is down be sure to 'stomp' them to destroy their skeletons, killing them permanently. (If one of them is destroyed by the headshot or sticky grenade, it smashes the skeleton automatically, so no need to stomp.) Knight Thralls are similar to the Mayan Thralls and Viking Thralls.