ὁ δαίμων, τοῦ δαίμονος god, divine being; evil spirit, demon

Remember the basic 3rd declension endings, which will be added to the stem of the noun.
As usual 3rd declension nouns (and adjectives) have 2 stems:
nominative: δαίμων
all other cases: δαίμον
Also as usual, dative plural ending will be -σι, but, for reasons of euphony, stem ν is dropped before σι
 
 
SINGULAR
  
 nominative           ὁ    δαίμων  
 genitive   τοῦ    δαίμον  ος  
 dative  τῷ    δαίμον  ι  
 accusative   τὸν    δαίμον  α  
 vocative  ὦ    δαῖμον    
     
PLURAL
  
οἱ    δαίμον  ες  
  τῶν    δαιμόν  ων  
  τοῖς    δαίμο  σι  
  τοὺς    δαίμον  ας  
  ὦ    δαίμον  ες