expirience-loss

Expirience loss is a mechanic which counteracts character leveling speed.
Possible variants of loss mechanics:
1.From damage sustained in battle, experience lost is calculated DamageTypeModifier*Damage*AreaModifier.
2.From character death 1/N of current expirience is substracted.
Levels are not lost, even if character has lower than level start exp.
3.From character death 1/N of current expirience is substracted.
Levels can be lost if character exp is below the level.
4.From cursed items or negative item modifiers which "bleed" exp from the player. The positive counterpart is items giving N exp per minute.
5.From specific exp-stealing spells/skills(used by monsters/players).
6.From area effects: some examples are "being in town/neutral area loses expirience 0.5/sec, being in hostile area gives 1exp/sec".
7.From time limits:Being in one area too long lowers exp, or reduces gained exp to near zero.(Anti-grinding mechanic).
8.From skill use: some skills/spells cost experience to cast.