Prius Online, a free-to-play fantasy title that featured a unique pet system comprised of anima and giga companions.
We first got wind of the title at last year's Game Developer Conference, and we covered its launch in the summer of 2011. In the interim, gPotato has decided to terminate the project and has posted a terse announcement on the game's official website with all the details.
March 27th will be the final day of service, and all cash shop items have been reduced to 1% of their original price for the last two weeks. gPotato is also compensating players via credit in its other games; you'll want to head to the compensation page to take full advantage of that offer by April 10th.
[Thanks to Dweeblok for the tip!]