Create an aging system that will automatically transform spawns from Young to Ancient over a period of time. Allow older spawns to create Young spawns and allow for the Older spawns to die. As a spawn ages, it's size could increase through each stage hit points could increase, dex could peak in middle age and intelligence could increase throughout. New abilities could be given to the spawn through each stage. A set value. For example: Poison Levels, Speed, Magic and Special Attacks. Loot could change with each level as the spawn ages. So, imagine walking down the road in Yew and you see a giant spider, on your way back through the city, you see the spider again and notice that it is bigger than it was before and moves faster. You avoid the spider and many hours later return to Yew. The spider is now larger than you are and is able to automatically web you and also has a few Giant Spiders around it of normal size. Besides the spawn becomming slightly larger they could transform, perhaps they would shake violently during their aging process and a giant spider might turn into a dread spider and in it's next stage, might only increase in hit points. If each group is broken down, for example: Arachnid, Elemental, it might be possible to add a graphic to each type in a dynamic system where you could basically work on 1 spawn and change the entire group. For example: An extra horn placed on a dragon, larger set of teeth. A certain blending of color so that you would not have to do each graphic but could add an indication of age and ability, perhaps a darker color that would then have lighter streaks so that if 1 dragon was changed to look as if it aged then any reptile could adapt the same type of appearance.