Advancement

The monster entry usually describes only the most commonly encountered version of a creature. The advancement line shows how tough a creature can get, in terms of extra Hit Dice. (This is not an absolute limit, but exceptions are extremely rare.) Often, intelligent creatures advance by gaining a level in a character class instead of just gaining a new Hit Die.

This material is Open Game Content, and is licensed for public use under the terms of the Open Game License v1.0a.