Just brainstorming some ideas for my recent design for Kiyo's Sentinel armor.

http://www.furaffinity.net/view/8276781/

Some people mentioned that being clad in full plate would be too heavy and restrictive for an agile character that can fly. Which is why I have decided that instead of using a metallic material, it is crafted from Dragon scales.
A requirement for an elite dragonkin chosen as a sentinel is to craft their own armor using scales shed from their body while in their transformed dragon state. These scales are as durable as steel while also being slightly malleable and lightweight. This gives them the full protection and maneuverability in their anthro forms as they do in their fully transformed states. The organic material also allows them to fully use their light based powers unhindered.

Biography:
The dragon kingdom is a world long corrupted by the demon attacks back in the dawn of civilization. Many of the dragonkin were affected by this and became the Dark dragons. Feral creatures that live on death and destruction. Only a small percentage of the race retained their sanity. Protected by the power of the lightwell. Bathing in these waters helps to stop them from succumbing to madness as well as giving them their trademark light powers.
To prevent further attacks from the Demons as well as to contain the corrupted dragons, the Dragon Aspect sealed off all the gateways leading to and from their world and went into eternal slumber. The uncorrupted dragons destined to live their entire lives in seclusion deep inside Mt Khoth where the Lightwell is located.
The only exception are the Sentinels. Elite dragonkin warriors who are sent to surrounding worlds to keep watch and prevent any other beings finding their way into their world. Possessing the ability to open their own portals to and from the dragon kingdom in select locations. This knowledge makes them a prime target for the demons who wish to conquer their world.
A sentinel mostly relies on stealth rather than combat. Their abilities allow them to distort the light particles around their body to cloak themselves to avoid detection. They can also create illusionary copies of themselves to confound their enemies, giving them an opportunity to escape. If these don't work, they then rely on their exceptional combat skills to fight off their attackers. They can draw on the powers of the lightwell that they absorbed when bathing in its waters to fire off charged blasts which they throw with deadly accuracy. They can also extend pillars of light from their palms to use as swords. One strike proving fatal against a lesser demon. These abilities must be used wisely since they are drawing from the very essence that prevents them being corrupted. Bathing in the Lightwell helps replenish it, but if for any reason the energy is fully depleted, they will permanently devolve into feral bloodthirsty dragons.

Hope you like the ideas that I have wrote down. Some parts may change in the future, provided I come up with better ideas, but for the time being, the foundation is pretty solid.