We meet most of these so called Syan Knights inside Drangleic Castle, before meeting the Looking Glass Knight. This and the fact about his armor leads me to think he was very important in Vendrick's eyes.

We can also note that Vendrick commissioned a shield for Sir Syan, but he died before it was finished. But he must have been important to Vendrick, who decided to make armors identical to his and give it to some of his knights - and they all turned mad soon after for some reason. He was known as the kingdom's most loyal knight, and was the one to lead the fight against the Giants when they attacked Drangleic. Now let's talk about someone else, Sir Syan. Note that the mirror the Looking Glass Knight uses as his shield is the same as the mirrors we find in Aldia's Keep, and they have the same effect: they are able to summon spirits from what seems to be another world. The armor also has wings on its back, which could be reminiscent of angels. The armor and weapons they wield have a common themes of thorns, which can be seen as a symbol of hardship and maybe martyrdom. I'd also like to adress the themes of its design - they are otherworldy and strange-looking. Even the official guide if we count it as canon only tells us that they are 'King Vendrick's lieutenant, charged with testing the prowess of those who seek to serve in Drangleic's order of royal knights.', and call them enigmatic. So, we have no idea who is behind the mask. They are able to summon spirits from other worlds. Their shield has special powers and is associated with the idea of parallel worlds: 'The Looking Glass at the castle is said to have been passage to another world.'. They are said to hold forever true to the King's command, meaning that they have been standing right there in the ruined castle ever since Vendrick fled at the apex of the war against the Giants. Those who fail the test are sacrificed by the merciless specular monstrosity.'). They are described as a monstrosity ( 'Those who wish to serve the king as loyal warriors must take the King's Passage and face the Looking Glass Knight. Obviously this is complete speculation, but fun to think about.ДЇirst, let's recap what we know for sure about the LGK: Hey, so here's a theory about the Looking Glass Knight's identity.

Mirror knight dark souls 2