Approved, but you may need to retcon having been turned Cahal at some point due to the lines in particular;
"Spell Point Buy only allows a person to stick to either Void or Exist, which is important in some cases, for example a Vampire, as Vampires can only have Void Magic as a Void Affliction."
"It is not possible to change Void or Exist alignment of Spells later, so it is important to make this decision before Point Buying Spells."
Them being a born void mage might be a retcon of that arc to an extent, so bare that in mind going forward.