This paper model is the Dagger of Xian, the main artefact that Lara finds in Tomb Raider II, created by Sascha Craft. It is a Chinese artefact and it was used by an evil emperor long ago to conquer his enemies. Legend says that once you plunge the dagger into your heart, you will be transformed into a ferocious dragon.
The Dagger of Xian is believed to be from the Qin period, hence it would be called Cheng'an instead. The Dagger of Immortality sounds more feasible, while the temple itself could be debated. However among most Chinese fanbase the term Xian in Tomb Raider II are always translated as 西安, the modern name of the city.
During one of the emperor's battles against an army of monks, one of the monks crept under the dragon emperor and pulled the dagger from his belly. The emperor was reduced to bone and died a horrible death. There was peace again. To prevent another war from happening again, the surviving monks took the dagger to rest in the Temple of Xian, at the Great Wall of China. There the dagger was locked up and remained in a slumber for many hundreds of years.
The dagger was retrieved by Marco Bartoli who plunged it into his heart. He transformed into the dragon, but he was ultimately defeated by Lara who pulled it from his belly after stunning him with her guns. The dagger since then resides in Lara's treasure vault.
Once plunged into the bearer's heart, after some time the dagger will transform the bearer into a dragon. The dragon's abilities include breathing fire and being invincible to gunfire. The only way to defeat the bearer of the dagger is to pull it back out of their heart, which in dragon form resides under their belly.
You can download this paper craft model here: Tomb Raider II - Dagger of Xian Free Paper Model Download