Mac Liu, a two-time founder with a background in tech rather than law, has raised $17 million for Arceus, an AI-driven law firm designed to deliver faster and more predictable commercial legal work as an alternative to traditional Big Law models.
The funding round was led by Greycroft, with participation from Craft Ventures, South Park Commons and other investors. The capital brings Arceus’s total funding to $17 million and will support hiring attorneys, engineers and AI researchers at its San Francisco headquarters as the firm expands beyond its initial focus on commercial contracts.
Arceus combines licensed attorneys with proprietary software and AI agents. The company focuses on reviewing, drafting and negotiating contracts for fast-growing companies, typically at a flat fee quoted upfront. It claims to reduce the time for a standard contract review from days or weeks to a few hours, with reviews taking longer than eight hours provided free of charge. Customers can submit contracts directly from tools they already use, such as Slack, rather than logging into a separate platform.
The AI layer gathers context from a company’s existing systems including HubSpot, Salesforce, Gmail and Slack to identify issues and route matters to the appropriate attorney. Founder Mac Liu has said the traditional billable-hour model creates misaligned incentives, as firms are rewarded for taking longer. His experience working with multiple law firms as a founder left him frustrated by missed deadlines, repeated explanations of the business and unpredictable costs.
Liu previously held tech roles at Robinhood and Anduril. He later founded Vultron, which built software for defense contractors, and sold the company earlier this year to govtech firm pWin. He retained the cash proceeds from that exit and is now deploying them into Arceus.
The approach is similar to other “new model” or AI-native law firms that build software for their own attorneys rather than selling tools to existing practices. Investors see a larger opportunity in rebuilding the firm itself. Greycroft partner Mark Terbeek noted that most of the legal AI market focuses on improving software for traditional firms, while Arceus is attempting to change how legal services are delivered.
Arceus said its customer base quadrupled in September. The firm is targeting startups and scale-ups that need commercial legal work done quickly and at predictable cost. Whether the model can scale beyond contract work while maintaining quality and regulatory compliance will determine how far it challenges established players.
