Experience level indicates the power of a unit relative to other units of the same type. Units advance their experience level by gaining experience.
A hero's experience level is expressed on a scale from one to six. Other units have only three levels: inexperienced, experienced (denoted by a silver medallion), and veteran (denoted by a gold medallion).
When a unit attains a higher experience level, they receive additional abilities and/or increase their stats. Heroes are able to choose how their abilities and stats improve, but other units are improved based solely on their unit type. A hero's upkeep increases by 
2 when they go up one experience level; other units upkeep remain the same regardless of experience level.
Difference from Unit Level
Edit
Experience level is easily confused with unit level, though they are quite different. Some of the main differences are
- Unit level describes a unit's strength relative to other unit types; experience level describes a unit's strength relative to the same type.
- Unit level only applies to non-hero units; experience level applies to all units.
- Unit level never changes; experience level may increase as experience is gained.
