Blanket is a type of Cover. Cover is related to Shell. 
Weaken is a type of Decrease. Weaken is a synonym of Lower. Lower is related to Better. Better is similar to Improved. 
Blanket --IsA--> Cover <--RelatedTo--> Shell 
Decrease <--IsA-- Weaken <--Synonym--> Lower <--RelatedTo--> Better <--SimilarTo--> Improved 