Dota 2/Davion the Dragon Knight

Dragon Knight is a melee strength hero who is usually played as a carry or a pusher. He possesses great pushing power using Breathe Fire, which can also be used for dealing AoE damage. He also possesses one of the stronger target unit stuns in the whole game with Dragon Tail, provided he can get into range. Dragon Blood gives him great durability, helping him survive large teamfights. His ultimate, Elder Dragon Form, is what changes teamfights. With it he can push towers, take teamfights and deal large AoE damage depending on his colour. Dragon Knight is certainly one of the easier heroes making him good for beginners, but his effectiveness in the hands of a master must not be underestimated.

Breathe Fire
Breathe Fire makes you breathe fire in a line at the direction of the target, damaging enemies hit by the fire. It is a simple but useful damage spell, good for pushing creep waves. It can also be used to damage multiple heroes in teamfights, though good positioning is required to land a good Breathe Fire.
 * Ability: Target Point, Target Unit
 * Damage Type: Magical
 * Damage: 90 / 170 / 240 / 300
 * Range: ~600
 * Mana Cost: 100 / 110 / 120 / 130
 * Cooldown: 12

Dragon Tail
Dragon Tail stuns an enemy. Its range increases to 400 while in Elder Dragon Form. It is the longest reliable stun when compared to other level 1 abilities, though you do need to be in melee range of the hero to use it, which can put you in danger. It is much easier to perform in Elder Dragon Form, as you can strike units further away.
 * Ability: Target Unit
 * Damage: 25 / 50 / 75 / 100
 * Damage Type: Magical
 * Stun Duration: 2.5 / 2.75 / 3 / 3.25
 * Mana Cost: 100
 * Cooldown: 9

Dragon Blood
Dragon Blood increases your health regeneration and gives you bonus armor. It is not a very interesting passive, but the bonuses it gives you is definately helpful. The increased regen and armor increases your survivability, which is vital since you're usually deep in the fray during teamfight.
 * Ability: Passive
 * Health Regen:: 2 / 3 / 4 / 5
 * Armor: 3 / 6 / 9 / 12

Elder Dragon Form
Elder Dragon Form transforms you into a dragon, the colour of which depends on the ability's level. All levels of dragon will increase your move speed and your attack range. At level 1 you turn into the Green Dragon which can do 20 magical damage per second for 5 seconds with your attacks. The damage over time cannot kill a unit, but it does affect buildings. At level 2 you turn into the Red Dragon that does splash damage with each attack. The further an enemy is from the attacked unit, the less amount of splash damage it will take. At level 3 you turn into the dreaded Blue Dragon, which not only has the same splash damage the Red Dragon has, but also a frost attack, which slows enemies move speed by 30% and attack speed by 20% for 3 seconds.
 * Ability: No Target
 * Duration: 60
 * Bonus Move Speed: 25
 * Bonus Attack Range: 372
 * Mana Cost: 50
 * Cooldown: 115

This transformation is very helpful when taking teamfights of when pushing. The Green Dragon is quite strong during the early-mid game with its great poison attacks. The Red Dragon is actually considered the least useful of the 3 dragons, since the pushing power of splash damage can be substituted with Breathe Fire. The Blue Dragon is obviously the strongest dragon there is, and its teamfight presence and pushing power cannot be underestimated. Its icy attacks will do ample damage to groups of heroes in teamfights, nullifying the damage output of carries and make escaping from you very difficult.