Quoting Andrew Knox
Good MOC, but explain- I never played Emperor's Tomb.
Okay, so Indy is looking for the second piece of the Mirror of Dreams, which will allow him to make it through the traps of the tomb of Qin Shi Huang. This piece is, apparently, in an abandoned castle in Prague. After getting through all the doors in the astrologer's clock, he enters the alchemist's lab, where he is promptly attacked by a homunculus. He chucks vials of acid at it and hits it with an acid-covered stick. When it's gone, he picks up the mirror shard from it's remains.