Red templars is an army in the Dragon Age video game series.
They are templars mutated and brainwashed by Corypheus thanks to red lyrium. The original templars are subordinates of the Chantry and are tasked with keeping peace and exterminating any danger to the world, such as heretics, mages, cultists and abominations.
In Dragon Age: Inquisition if the Templars aren't recruited by the Inquisitor (the protagonist) the templars are all either murdered or corrupted and under command of Samson (Dragon Age).
If the Inquisitor recruits the templars then has a choice to preserve or disband the order. It doesn't prevent existence of the red templars but at least stops production and rest of the templars remain uncorrupted and ready to avenge their brothers and sisters in arms.