Edge is related to Cream. Cream is a type of Modify. Modify is etymologically related to Mode. Moderate is derived from Mode. 
Introduce is the opposite of Say. Say is related to Pay. Pay is related to Debt. Debt is related to Obligation. 
Edge <--RelatedTo--> Cream --IsA--> Modify --EtymologicallyRelatedTo--> Mode <--DerivedFrom-- Moderate 
Introduce <--Antonym--> Say <--RelatedTo--> Pay <--RelatedTo--> Debt <--RelatedTo--> Obligation 