Curtain is a type of Barrier. Curtain can be used for Dark. Dark is the opposite of Fair. 
Theological is derived from Theology. Theology is a type of System. System is related to Rank. Rank is related to Standing. 
Barrier <--IsA-- Curtain --UsedFor--> Dark <--Antonym--> Fair 
Theological --DerivedFrom--> Theology --IsA--> System <--RelatedTo--> Rank <--RelatedTo--> Standing 