Soul Piece Based Transformations

Queen Syakonnia surprised to see Astarte in a semi-reptilian form (semi-reptilian because full reptilian would make her look like a humanoid lizard monster with a lizard head and a flat chest). Astarte showing Syakonnia the power of Xerxes' soul pieces in easing transformations, which Astarte has an interest in. 

Xerxes' soul pieces have been shown to be powerful. Astarte's use of these soul pieces is as a magic amplifier allows people to transform into stronger tougher versions of themselves with ease. This is the reason why soul pieces are valued, even by people who don't know that external soul pieces have this ability, and especially ones from powerful people like Xerxes who Astarte has an interest in. 

A Picture from Xer-Xer's character profile. Showing two transformation chambers with two Digyokatu (meaning big river people in Anatropa). This is how the Astart empire usually makes "enhanced Jamesianoids". This way of transforming people is long expensive and it takes as much effort to transform back and not only that, the elite forces of the Jamesians, the Knights of Ahura-Mazda have become adept at finding and destroying the chambers. Jamesianoids needs to stay in transformation chambers for days in order to transfroms. Xerxes' soul pieces are able to make this process as quick as it seen on Pages 73 and Pages 74 of Xerxesian Chronicles: Astarte's Challenge.

Queen Syakonnia after a quick soul piece transformation into a Tozatu (lizard person in Anatropa). One of Xerxes' soul pieces can be easily seen on the back of her head glowing as she uses it to power her magic. 

Why would someone even bother with transforming themselves into lizard people to fight the Jamesians and combat Xerxes?

There are many reasons that Jamesianoids might want to transform themselves. The biggest reason is that the transformations make them stronger and more durable. As Syakonnia skin becomes impervious to most weapons and she can wrestle Xerxes' shield off him with ease.

Xerxes trying to stab Syakonnia but his sword cannot go though her soft yellow belly skin. Syakonia is about to grab Xerxes' shield and grab it off him.