When a vicious king threatens the peace between the Gifted and Commoners in Athenia, a red headed thief, participates in an illegal ritual where she discovers, she is the last Moonkeeper. To stop the evil in the kingdom, she must take help by an angry warrior, a gold hearted prince and the next king in line with horrific powers, before the world as she knows it, disappears.

It appears as if you have two inciting incidents; 1) A vicious king threatening peace, 2) she discovers she is the last Moonkeeper. So, I believe you have two options – 1) start with – When a vicious king threatens war, the last Moonkeeper must… – or – When a thief discovers she is the last Moonkeeper, she must stop a war by…

Also, you have a included a physical description (Redhair), which may have some significance in the story, but for us readers of the logline we have no idea what relevance it has so it is redundant. For loglines, it is recommended to stick with character descriptions i.e. hotheaded, adventurous, dutiful