While toy unboxing videos continue to rack up millions of views on YouTube, Loot Crate, the L.A.–based e-commerce platform that delivers themed mystery boxes to kids on a monthly basis, has raised US$18.5 million in Series A funding.

The funding round was led by Upfront Ventures, with participation from Breakwater Investment Management, Time Inc., Downey Ventures, M13 and SterlingVC.

Loot Crate boxes are sent to 600,000-plus subscribers and contain branded items based on entertainment and pop culture franchises. Each box, which costs roughly US$12 per month, offers up to seven licensed products (the majority of which are Loot Crate-exclusive items) and content that ranges from collectible figurines to comic books and apparel.

The company has also created a new online channel for fans to discover new and established brands, while providing entertainment companies with a new direct-to-consumer distribution platform. The Loot Crate channel is kicking off with an integrated promo featuring Microsoft’s Halo franchise, wherein the two companies will team up to deliver an exclusive game-themed box to Loot Crate subscribers.

Loot Crate launched in 2012 with US$25,000 in seed funding, and the company’s annual revenues have since grown to more than US$100 million. Loot Crate currently ships to 35 countries, including the UK, which has become its second-largest market (after the US) and will be opening offices in the UK this summer.

The investment from Upfront Ventures also sees firm partner Greg Bettinelli join Loot Crate’s board of directors. David Voss, former SVP of Mattel’s Playground Productions, was tapped as chief creative officer earlier this year.