Here's a nice list of ideas concerning that:
- In the resting chamber, better creatures could be accommodated and/or resting time could decrease.
- The training room could unlock abilities and at a later level it could increase attack speed, increase defense and perhaps allow creatures to attract money from opponent creatures when they kill.
- The prison could hold higher level creatures (more secure).
- The library can research higher level spells, or perhaps spells of a different branch.
Thoughts?