Erin Blakewood

Erin Blackwood is a new student  in  The Touchstone of Ra. In the promos, it  is shown she will have something to do with the mystery. Not much is known about her until the Touchstone of Ra airs. In the UK Promo Erin is seen standing next to Cassie, Mara and Dexter helping Sibuna. In the special, she becomes a member of Sibuna, along with Cassie and Dexter.

Personality
Erin Blackwood seems to be very intelligent, and a bit like Mara, as she was known as a hard working student when the series started. She brings in a poster of The Periodic Table of Elements when she moves into the Anubis House, which also supports the prediction that she's very intelligent. She could also be slightly smarter than even Mara, as she quickly realises that Sibuna is Anubis backwards, something that Mara did not notice.

Cassie
 (Unknown-Present; Friends) 

When moving into the Anubis House in The Touchstone of Ra, it seems that they're sharing a room. Also, in the special Anubis Unlocked: The Touchstone of Ra, it shows Cassie and Erin under a table. It's possible that Cassie and Erin are very different, as in it's possible that Erin's strives to be intelligent as you can see in The Touchstone of Ra she's hanging up a poster of The Periodic Table of Elements, and that Cassie is very fashionable as you can see in The Touchstone of Ra, as she brings a lot of clothes with her to the house. (See Cerin)