Here are the minor chacters that had a significant role in the story even if some of them were barely mentioned:

David

A member of the resistance, he is the one who found Gemma in the caves of Gelid and contacted Keylla.

Sinead
(Lady-in-waiting 1)

One of the ladies residing in Vigoreaux castle. Some believe that she will be the one to marry king Roni, that is if the monarch wants to settle down any time soon.

Liesserl
(Lady-in-waiting 2)

She is one of the ladies-in-waiting to reside in Vigoreaux castle, it's no secret that she is obsessed with the king, and his attributes.

Guinevere
(Lady-in-waiting 3)

She is one of the ladies-in-waiting residing in Vigoreaux castle, she spends most of her free time in the kitchen. Preferably taste-testing the dishes to ensure that the king doesn't get poisoned, though it's very unlikely for the king to get poisoned in his own castle.

Irene
(Lady-in-waiting 4)

She is one of the ladies-in-waiting who reside in Vigoreaux castle, the youngest out of the four and most likely the most reasonable out of the others.

The Matron

The beloved mother figure of the Vigoreaux twins. She has served the Vigoreaux kingdom since the previous king was only a child.

Aaron

The leader of the resistance, the Reigniters, he accepts Gemma to become a member of the resistance and plots their next move against the Empire.

General Theo

One of the Empire's generals, only mentioned in chapter 4.

Emperor Erthil

The figurehead of the Erthilean Empire.