The Summoning Compass is Harry Greenwood's personal artifact used to call out to Elder Charity Callahan when her presence is needed.
Harry tried to summon her with the compass after the Charmed Ones caught the Harbinger of Hell, but she didn't arrive until days later.
On the day of the exorcism, the Harbinger broke out of his confinement. Maggie used the compass to summon Charity for help; she arrived instantly and tied down the demon.
Mel later used it to summon Charity in order to talk to the Elders about the Sarcana.
- Despite the name, the compass' only purpose was to call out to Charity. She would then portal to the summoner's location.