Raphael Santiago: It contains Camille’s grave dirt.

Magnus Bane: Grave dirt? I thought maybe diamonds, or that gold ring she stole from Cleopatra’s tomb.

Simon Lewis: So we’re excited about a box of dirt. Anyone wanna clue me in?

Magnus Bane: If you have a vampire’s grave dirt, you can use it to summon them.

From Shadowhunters – Season 2 Episode 4: ‘Day of Wrath’ (2×04)