Large language models (LLMs) are reshaping interactive digital narratives (IDNs). However, creating complex interactive narratives while preserving narrative consistency remains challenging. We present Orchid‑Creator (Orchid), an LLM-based authoring tool that represents IDNs as story graphs with a card‑based interface for scene definition and conditional transitions. We evaluated Orchid in two studies: a usability study with eight authors, and a comparative study with 20 participants (authors, developers, and players) that compared Orchid to Twine and AI Dungeon. Authors reported that Orchid’s features met their needs (card‑based interface: 4.0/5; story graph: 4.38/5; variable setup: 4.5/5). Structuring narratives with Orchid was easier (M = 6.0/7, p <.01) and produced better‑structured stories (M = 5.3/7, p <.05) than the alternatives, balancing author control (M = 5.5/7) with outcome diversity (M = 5/7, p <.01) and maintaining comparable usability. Finally, a case study with an artist demonstrates Orchid’s utility for interactive art.

Integrating Large Language Models (LLMs) into Interactive Digital Narratives (IDNs) enables dynamic storytelling where user interactions shape the narrative in real time, challenging traditional authoring methods.This paper presents the design study of Orchid, a creative approach for authoring LLM-driven IDNs.Orchid allows users to structure the hierarchy of narrative stages and define the rules governing LLM narrative generation and transitions between stages.The development of Orchid consists of three phases.1) Formulating Orchid through desk research on existing IDN practices.2) Implementation of a technology probe based on Orchid.3) Evaluating how IDN authors use Orchid to design IDNs, verify Orchid's hypotheses, and explore user needs for future authoring tools.This study confirms that authors are open to LLM-driven IDNs but desire strong authorial agency in narrative structures, highlighted in accuracy in branching transitions and story details.Future design implications for Orchid include introducing deterministic variable handling, support for trans-media applications, and narrative consistency across branches.