The purpose of the passage would be to Compare Antigone situation with Danae's. Since the purpose of an Allusion is to recall something without actually mentioning it it would be talking about Antigone but doesn't mention her. A keyword would be the word too meaning a comparison between two things. >>> "In her brass-bound room fair Danae as well endured her separation from the heaven’s light, a prisoner hidden in a chamber like a tomb, although she, too, came from a noble line."