Consult the Help page, in particular the Character Attributes as there are differences between the games. Here is a snippet from Viking Clan relating to level ups.
Leveling Up
Each time you reach a new level, you will receive bonus health, energy and stamina from the Gods. For lower levels, they will be refilled completely, for the higher levels they will receive a maximum of 5000 health, 500 energy and 50 stamina up to your characters maximum.