Beyond The Sapphire Gate R.V. Johnson

Coming into her power in adulthood, Crystalyn activates a curtain of darkness between a pair of sapphire obelisks with a travel symbol. Her younger sister Jade, the one person she cares most about having raised since their mother's disappearance, touches the gateway and vanishes. Crystalyn follows, developing her strength in a land where strife, warfare, and magic use are rampant.

The search for Jade grows ever desperate as Crystalyn learns each use of magic is killing her, her mind deteriorating. Though a political Circle of Light made up of mystic users, a Dark Citadel of warlords, and a Hundred Season war block the way; she must go on.

Time is fast flowing away from both her and Jade; with far more at stake than they both realize.