When playing KingsRoad, there are two bars you will need to carefully manage to ensure success: Health & Mana.
The Health Bar is the red bar on the left, and is just that: how much health your character has. This equates to how much damage your character can take before dying. Mousing over the Health Bar will display current health and total health in numerical values. Health is lost as the enemy deals damage to your character, and your character will die when the Health Bar reaches zero. Health is replenished through the consumption of foods and certain elixirs, and may also be regenerated naturally over time (dependent on what passives are allocated on that class). The Health Bar will also be completely refilled whenever you level up. The amount of total Health available is dependent on the level of your character and on the bonuses received from equipment, passive abilities, and buffs.
The Mana Bar is the blue bar on the left, and displays the mana available for your character. Mousing over the Mana Bar will display current mana and total mana in numerical values. Mana is what fuels all the Skills available to your class; each Skill uses up a certain amount of Mana, and once the Mana Bar reaches zero, no further skills can be activated. Some Skills will cost a fixed amount per use of the Skill, and other Skills stay activated, using certain amounts of Mana over time. Any Skills that utilize Mana over a period of time will be deactivated should the Mana Bar reach zero. Mana can be replenished by consuming drinks, and also from certain elixirs; it can also regenerate naturally over time (dependent on the passives you're using). The Mana Bar will also be completely refilled whenever you level up. The amount of total Mana available is dependent on the level of your character and on bonuses received from equipment, passive abilities, and buffs.