There is no such thing as leveling up in Gehenna, however if the GM deems the occasion fitting, they may allow players to increase their skills, and even choose new feats and spells.
This may be because a player has finished reading an informative book, or has experienced quite a bit of change throughout their journey
Players may choose two skills + their INT modifier, that they want to increase. Once chosen, they must roll 1D6 against each of their skill scores. They may add their INT modifier to their result, in order to aid their success. If they roll higher than their current score, then their score increases by +1.
If they roll lower than their current score, then their score remains. This means that the more you improve in a skill, the harder it will be to continue improving.
Accquiring Class Features & Spells
Players may also accquire 3 Class Features and Spells that they don't possess by replacing ones they currently utilize.