There are three classes of Dragons in the game - Hunter, Warrior and Sorcerer.
Hunter - These dragons have a fast tap fireball attack. They have a strong burst damage and spells such as Cloak and Evasion that allow them to penetrate deep into the enemy defenses. These dragons are extremely good at taking out strategic targets on the enemy base.
Warrior - These dragons have a flamethrower attack. They have a lot of health and spells that keep them alive for long such as Rejuvenate, Cure Poison, Stoneskin Shield. Warrior dragons are great at cleaning out large sections of the enemy base.
Sorcerer - These dragons have a swipe and lock-on attack that can target up to three towers simultaneously. Sorcerer dragons have very powerful (but expensive!) spells such as Fireball, Summon Minion, Invincibility. These dragons are very effective against dense group of towers and when you have built up rage from previous rounds
Invoker - Invoker Dragons have 4 breath ammo total: the first 3 will shoot a projectile at enemies, while the 4th tap will discharge an “empowered shot”, which will provide a special attack, disabling effect, or other advantage in battle. This empowered shot’s effects and damage output will vary across different Invokers.