Traps are set to protect the tombs from the tomb raiders. Plus, there might me some guardians and mommies and these stuffs but I don't really believe in those thing...Hope I Helped...
In my opinion tomb raider underworld is much better than tomb raider legend because you learn alot more about Lara in this one especcially because her devotion to finding her mother is much more...
Yep there is a game called beneath the ashes and there is one called Lara's shadow but they are add-ons, there is one called Lara croft and the guardian of light which is a proper games, not a add-on...