Experience; a lever of how much you have attained from your mistakes. When talked about, it is often abbreviated to exp.
Heroes gain experience points mostly by defeating Monsters, although there is a profusion of other ways too. When heroes gain enough experience points, their level increases and they become more powerful; more battle-hardened.
To see how the needed experience to level up, look on the pantheon of might and find out the total experience (in the last column) which is the highest without being in the next level band.
Experience comes in two main forms; Starite and Monstite.
Starite is the rawest form of experience in existence when freshly mined from the "Caves of Leveler". It is purple in color, and in this state it is useless to any hero, strong or weak. However, it has a distinct flavor which most monsters would (and do, usually) kill for. Once it has been digested by a monster, it transforms into Monstite, which is a fine golden dust that stays inside the monster.
It is also very useful to heroes, but must be gained by killing the monsters to release it from them. Greedier monsters (usually the fatter ones) provide the most experience because they are most likely to have eaten more Starite. More powerful ones also have a lot since they have survived longer and therefore have ingested more of it.
Experience also rarely appears in Questite and Itemite forms, too.
Questite is the most unusual of experience because it is formed by the feeling of (purest) accomplishment, which can only be obtained by completing a difficult task. It's color and shape are specific to the hero, many heroes also say it smells slightly like peppermint. This is very high-level experience form and gram for gram is worth ten times more than Monstite.
Itemite is formed by magic inside special items. It is usually blue in color and it's quality is unknown, because it can either absorb or radiate experience. Heroes who encounter this should beware for this reason, as Itemite is very, very unpredictable.