In its own way, its no more unnatural than any update in Terraria history. Those in charge formed an idea, imagined it in the Terraria world, and pursued the course which would allow that idea to happen. Just this time, it involved collaborating with another company.
Which isn't so unusual . . . Terraria has crossover content with several games, including Edge of Space (which features Skeletron Prime as a boss!), Pixel Piracy (which has Terraria content, and content of its own which is now in Terraria), as well as the more minor approved content references to Minecraft and Portal in Terraria. Not even a year ago, we collaborated with the developers of Chivalry to do a cross-over art contest. There is often a lot of camaraderie between indie developers, and Terraria has a pretty significant history of making and receiving these gestures of good will with other companies. This just happens to be the most significant in scope, but its certainly not the first of its kind.
Which isn't so unusual . . . Terraria has crossover content with several games, including Edge of Space (which features Skeletron Prime as a boss!), Pixel Piracy (which has Terraria content, and content of its own which is now in Terraria), as well as the more minor approved content references to Minecraft and Portal in Terraria. Not even a year ago, we collaborated with the developers of Chivalry to do a cross-over art contest. There is often a lot of camaraderie between indie developers, and Terraria has a pretty significant history of making and receiving these gestures of good will with other companies. This just happens to be the most significant in scope, but its certainly not the first of its kind.