Nintendo Co.'s two-year old experiment in mobile gaming is heading for uncharted territory with Dragalia Lost, its first smartphone title featuring original characters rather than its established stars.

Co-developed with new partner CyberAgent Inc., the free-to-play game is debuting Thursday on Apple and Android devices across the U.S., Japan and Asia. Instead of relying on an all-star lineup of characters like Super Mario and Donkey Kong to generate buzz, Nintendo is betting on a completely unknown cast of heroes and a new fantasy world full of dragons.

That's a big gamble — and the early signs are worrisome. Fewer than a million players preregistered to download Dragalia Lost. Nintendo's Super Mario Run for mobile devices notched up more than 20 million registrations prior to release in late 2016. Dragalia Lost went live Thursday afternoon Japan time.