Every player starts with 3 heroes. The combination of heroes awarded is random, but their stats are the same for every player. The main motivation for this is to create variety for the PvP part of the game, and also to introduce more characters to a wider player audience. Each player will begin with one fire hero, one water hero, and one air hero.
There are 8 possible combinations:
Illusionist - Valkyrie - Alchemist
Illusionist - Valkyrie - Sorcerer
Illusionist - Empress - Sorcerer
Illusionist - Empress - Alchemist
Knight - Empress - Sorcerer
Knight - Empress - Alchemist
Knight - Valkyrie - Sorcerer
Knight - Valkyrie - Alchemist
Every player also gets the Necromancer (tank) as a reward for beating Thornwood.
Every player will also rescue the Jester after level 3 in Mount Flame.
We hope this clarifies!
Note: The three heroes you do not start with from this list are available later in the game after collecting enough Hero Shard.