Arceus

Arceus is a law firm for fast-growing companies that quotes a flat price before any work begins, with licensed attorneys reviewing every output alongside AI agents and software built in house. The firm provides legal services to fast-growing companies at a flat price that is quoted before a matter begins, and licensed attorneys approve every piece of work with help from AI agents and software Arceus built itself. Most of the current work covers commercial contracts such as master service agreements, NDAs, and vendor deals, with a standard contract review listed at $500 and capped at eight hours of attorney time before the client stops paying. The launch matters because it lands as legal AI tools proliferate inside existing firms, while Arceus is attempting the harder path of rebuilding the firm itself around that software. Attorneys work inside an internal operating system called CounselOS that tracks each client's preferences, past agreements, and negotiation history, and pulls context from Salesforce, HubSpot, and Gmail so new matters start from what the firm already knows about the business. Clients get live progress updates through Slack and email. The company says its customer base quadrupled in September, and some clients have started routing employment and privacy matters over as well, with the longer-term aim of covering every legal need a company has. Founder and CEO Mac Liu started Arceus after cycling through multiple outside firms as a founder himself and running into missed deadlines and bills that ran over estimates, which pushed him away from the billable-hour model. The $17 million round was led by Greycroft, with participation from Craft Ventures and South Park Commons. The capital will fund hiring of attorneys, engineers, and AI researchers at the San Francisco headquarters as the firm expands into new practice areas.