The Undying Queen: Emergence. Undead Queen, #1

She was sold to the military by her own brother. Two years of hell. One earned rank. And enough trust in the institution that trained her to walk into a commanding officer's tent unarmed. She was wrong to. When the Colonel makes his vile intentions clear, Private Marianne Silvers has no weapon, a 103-degree fever, and nowhere to run. She fights back anyway. It costs her everything-until a blood-red summoning circle tears open beneath her feet, and her world disappears.
She wakes in a castle that smells of rot and old power, reborn with the scales of a Dragonborn and the weight of 940 sacrificed souls on her shoulders. This new world is at war. The Undying Queen-ancient, feared, and commanding legions of the dead-is losing ground to an army of "heroes" called from other worlds to wipe out demonkind. Maria has landed on the wrong side of that story. Or maybe she hasn't.
Refusing to be a pawn in another ruler's war, Maria steps out into the wastelands to uncover the truth for herself. And the more she learns about the human alliance and the gods they serve, the more the demons start to look like the honest ones. Dark isekai fantasy for readers who want morally complex heroes, genuine stakes, and a queen worth following into the dark.