Well Rashak, you bring up a good point- a point that I've used in my campaign. The lizardmen empire has become quite lazy and overfed. Their kingdom has spread over a large area, and their king is nearing death and he has numerous offspring that are vying for control of the throne once he dies. This has also caused political battles within the lizardmen empire.
On top of it all, in recent years the elves in the northern camps have managed to stage a successful revolt and have reclaimed parts of their homeland.
Many camps still remain in the heart of the lizardmen empire though, and the elves are attempting to build their armies in order to stage a D-day type assault upon the lizardmen empire and free their brethern. In the meantime, there is a system among the elves that selects certain individuals to undertake dangerous missions into the heart of the lizardmen empire in orer to rescue important elves, assassinate lizardmen officials, etc.
-mac1504