A Dragon does short-range splash damage when he attacks. This can only be noticed when used against Clan Castle Troops and Walls.
The purple Dragon icon shown in the Barracks is actually a level 2 Dragon. The Dragon changes from green to purple after upgrading, matching its image in the Barracks.
Dragons have no preferred target when attacking; they will simply attack the closest building to them. However, once they become aware of enemy Clan Castletroops, Heroes or Skeleton Trap skeletons (either by being attacked themselves or being near another friendly troop under attack), they will leave their previously targeted building and engage the enemy troops instead. Once all of the nearby enemy troops are defeated, they will proceed to attack the nearest building from their current location.
Most Dragon strategies involve taking out as many Air Defenses as possible with other units (infantry, Giants, etc.) or Lightning Spells, as it is a significant weakness to this powerful unit.
Dragons are mostly used to get Trophies and in war as their high cost doesn't make them great candidates for resource raiding.
When using mass Dragon raids one should be careful of Buildings in the corners because their relatively slow movement speed does not make it great for moving around from corner to corner. To prevent this, attackers should bring some Barbarians or Minions or save their Barbarian King to take out lone buildings in the corners; it might mean the difference between a 99% 2-star and a 100% 3-star raid.
Dragons are one of the most powerful Troops in the game, and as such it can be difficult to defend against them. Multiple high-level Air Defenses are critical for success against Dragons.
As a Town Hall 8 player, keeping your Air Defenses semi-spread while protecting them with Storages and other high hitpoint buildings is the key to preventing most 3-star attacks using Dragons. If the Air Defenses are too close together, a single Rage Spell applied to a cluster of Dragons can quickly wipe out all three.
Dragons are wonderful Clan CastleTroops. As a flying unit, the Dragon is completely immune to attacks from most ground troops, and his splash damage capability makes it especially suited for destroying groups of Barbarians and Goblins. His high health also helps him survive attacks from even multiple Archers or Wizards (although a large group of either will usually be enough to destroy the Dragon).
The Dragon encounters major graphic changes at every level.
Level 1 Dragons have green-colored skin and black eyes.
At level 2, the Dragon's skin turns from green to purple, matching his image in the Barracks. His eyes also turn the color of elixir.
At level 3, the Dragon's skin changes again to dark grayish-brown.
At level 4, the Dragon's skin turns a deep red; as part of the update announcement, Supercell referred to it as the new "ancient red dragon." His eyes also start flaming.
At level 5, the Dragon's skin turns into a brownish-crimson color. It also obtains golden horns near the back of its head and spikes on its back. Its wings also gets larger.
The first person to have reached over 4,000 trophies (Jorge Yao) used an all-Dragon army to do so. He used 4 Lightning Spells as support, one to take out Clan Castle troops and the rest to destroy an Air Defense. This was his way to ensure 50% damage practically every time he attacked in order to become the top player and achieve this wonderful feat.
You can have a maximum of 12 Dragons at one time in a complete set of fully upgraded Army Camps. This number increases to 13 if you include the 1 that can fit into a level 3 or higher Clan Castle. On the battlefield, you can clone an additional 2 Dragons with two level 1 or higher Clone Spells.
The Dragon's attack was given a splash damage component as of the 12 March 2013 update, making them much more powerful against groups of ground troops.
The Dragon received new art as of the 23 May 2013 update; the new Dragon receives forelegs along with a line of small spikes down its neck and back. This new look is often debated among fellow players to which one looks the 'best', along with the P.E.K.K.A.
The Dragon has a pair of paws and fire in his mouth since the 23 May 2013 update. The appearance has also been changed to a robotic like creature.
A Dragon's shadow is oval, not dragon-shaped.
The Dragon's upon-death skeleton is human-shaped.
The Dragon is one of only two troops to have different appearances at every level (along with the P.E.K.K.A).
The level 3 and 4 Dragon has a very thin see-through line going through the base of the wing. However, this is barely noticeable.
Dragons do not attack Walls, but can deal damage if indirectly attacking (Shooting at Clan Castletroops over a wall, etc.).
The January 2013 update added Dark Elixir, stating that this resource is formed over aeons from fossilized Black Dragon (then-maxed level 3 Dragon) bones. However, no levels of Dragons are trained or upgraded using Dark Elixir.
Part of the May 4th 2016 update, the Dragon's training time has been decreased from 30 minutes to 15 minutes.