Pulsemage Advocate does not have summoning sickness.
Steps
Activate Altar of Dementia by sacrificing Coercive Recruiter, causing target opponent to mill cards equal to Coercive Recruiter's power.
Activate Pulsemage Advocate by tapping it and putting three cards from an opponent's graveyard into their owner's hand, returning Coercive Recruiter from your graveyard to the battlefield.
Coercive Recruiter enters the battlefield, untapping Pulsemage Advocate.