[1][2] Marcia is described as a tall woman with characteristic green wizard eyes and long, dark, wavy hair.

Marcia also wears a pair of pointy purple python skin boots made for her by shoemaker Terry Tarsal.

The Marcia character was key in Sage's development and continuation of the Heap series, as she motivates a lot of Septimus's decisions.

When Jenna is ten, Marcia takes her away with the assistance of Silas, his son Nicko and a "Young Army" boy called 'Boy 412'.

One day, Marcia receives a message from Silas and goes back to the Castle, but it is a trap and she is caught by DomDaniel's guards.

Boy 412, assisted by Jenna and Nicko, board DomDaniel's ship and a fight ensues which results in Marcia taking back her amulet and escaping on the Dragon Boat.

In Physik, Marcia comes to learn that Septimus has been sent back in time by being pulled through a magykal looking glass in the Queen's Room by Marcellus Pye.

In the meantime, an evil Queen Etheldredda's spirit (who sent Septimus back) gets released by Silas Heap when he unseals her portrait and wreaks havoc on the Castle.

Marcia, on learning Etheldredda's evil plan to kill Jenna so she can be queen forever, decides to destroy her.

Marcia prevents this by helping Septimus escape, assisted by Jenna and his friend Beetle, who discovers that going to the House of Foryx will enable them to find Nicko and Snorri.

Septimus immediately jumps at the chance to take leave meet up with Jenna, Nicko, and Snorri (who stayed behind across the sea with Milo Banda), and Marcia reluctantly lets him do so.

At the end when Tertius Fume attempts to murder Marcia with an army of warrior jinnee stolen from Milo.

With several swords at Marcia's throat, Septimus and his own jinnee - Jim Knee - race to freeze the whole army, and save her.

She modifies Zelda's desk by adding hands to it in Magyk or cleaning up the scribes mess in a trifle in Queste.

Among Marcia's dearest possessions are her purple python skin boots which she has stockpiled after her favorite ones were ruined in events from Magyk.