Complex sentence: Thief tries to steal from a giant chest only to be confronted by the ordeal of Avarice, however he flees as Black Mage enters the room (finally having got through the door).
Split into simpler sentences: Thief tries to steal from a giant chest only to be confronted by the ordeal of Avarice. However he flees as Black Mage enters the room (finally having got through the door).