Upon gaining the requisite number of experience points, a character may increase in level after completing a period of training under the tutelage of a more experienced teacher or, at higher levels, by study or practice. In general, the cost of training will be quite steep, even if the character is high enough level not to need a tutor.
The cost of training will be approximately 1,500 gp per level, and will require 1d4 weeks to complete. Alternatively, the GM may assign a number of weeks of training based on his or her evaluation of the player's and character's performance.
Random Experience Variable (Optional Rule)*: If this optional rule is used, the number of experience points required to gain a level is somewhat variable, representing the vagaries of a character's individual experiences as an adventurer. The base number required to gain a level of experience, shown in the description of each character class, is modified for each level of experience by a random factor. There is a 50% chance that the base number will be reduced, and a 50% chance that it will be increased. Roll a d20 and multiply the result by the level to be attained to determine the exact amount by which the base number will be adjusted.
*This optional rule is excluded from the Designation of Open Game Content.