right-hand man 
noun
An indispensable helper or chief assistant.Calderwood can't help but tackle things head on, though, and he is ably assisted by his right-hand man, whom he refers to as the silent assassin....
- Heath, ably assisted by his right-hand man Guy Rich - now in the Premier's Office - soon became bigger than the unit itself.
- All of a sudden, his right-hand man, former Chief Councilman Kermit walked in, without any warning whatsoever.
- prescient
- pre-scientific
- presciently
- prescind
- prescission
- pre-score
- pre-scoring
- Prescott
- prescreen
- prescribable
- prescribe
- prescriber
- prescript
- prescriptibility
- prescriptible
- prescription
- prescriptionary
- prescription book
- prescription drug
- prescription glass
- prescriptionist
- prescription medicine
- prescriptive
- prescriptively
- prescriptiveness