The Dreadwater Gate. The Inkweaver Archive, #2

Born Nameless. Raised in ice and snow. Destined to rule. Arya Nameless has sidestepped her destiny in favour of joining House Ravenstrike and helping Thiara Ravenstrike become High Warlord of Dunidaen. First, Arya must ensure that Thiara's only son, Rorin, succeeds in running the Dreadwater Gate into Khadini, a deadly rite of passage that none have survived for decades. If they triumph, Arya will be named general of Ravenstrike's army and land a political blow against their powerful adversary, Warlord Mathas Crowtalon.
Yet Khadini holds challenges far beyond what they expected. And while Arya contends with wild jungles, fierce enemy warriors, and potential new allies, the Nightstalker continues to seek her with relentless intensity. The monsters hunting her wield a dark magic she has no way of countering. Survival relies on staying hidden, secret. Yet, when Arya's wyvern calls, the time for hiding is over. Because destiny cannot be ignored forever.