Okay, I broke a purple ball in the corruption.
What dose that do?
You have broken one of the pillars of the world which hold up the sky. Now a star might fall to earth and spawn strange alien beings until you clean up the mess you made.
That's actualy a realy nice way of expaining it. Please, continue.
Very well.
In ages past, two forces warred in the void. The Corruption, vile forces of darkness and dispair, were the remnants of an ancient civilization which had mastered biological engineering and their own mortality and now sought to conquer all other worlds and remake them in their own image. The Hallow, exalted beings of light and purity, were the personification of the immanent vital force of the universe and violently opposed what they perceived as the madness of the Corruption. Amidst all of this fighting, millions of innocent worlds died horrible deaths as each side excused the mounting atrocities as acceptable losses necessary to win the unwinnable war.
This is the background for Terraria.
So what makes the world of Terraria different you ask? Well that would be Bob. No, that isn't the little person you play... Bob is a defector. Once a highly regarded scientist and scholar among the ranks of the Corruption, Bob has grown weary of the war and the fighting and the constant trampling and slaughter of innocent beings underfoot. So Bob uses his vast knowledge and power to seal away a small bit of the cosmos from the two opposing elemental forces of the universe.
Like drawing a curtain against the nightime mists, Bob constructs a veil over the world which keeps out all which should not be and allows an unmolested world to seed and grow. From genetic stock gathered from hundreds of crushed and broken worlds, Bob seeds this new world with all manner of plants and animals. As time goes on, life prospers and finds its own balance. When the world is judged ready, Bob introduces people. Sapient beings ascended from apes on a long-lost world of blue seas and white clouds, now shattered and burned to a cinder by the unrelenting warfare. These people prosper as well, living from the land and working in harmony with the natural balance which has been achieved.
All but one, anyway... all but Steve. But we'll get to that soon enough.
You see, Bob's veil was solid but he was not exactly thorough when he created his pocket paradise. The smallest seeds of Corruption managed to creep in at the last moment and a few areas of the world of Terraria began to change for the worse. Bob was unconcerned, however, as these small bits of Corruption would eventually wither if not fed. Besides, Bob had a plan of his own! Thus Bob created the Goblins, a race of sapients ascended from a species of particularly clever underground shrew. Bob charged the Goblins with maintaining the balance of the world. They would make their home within the far distant hills beyond the great oceans and march out against anything which threatened this fragile balance. They would make daring raids against the Corruption which limited its growth and would occasionally plant Sunflowers, a species of Hallowed plant which had also been mistakenly included in Terraria but caused no adverse effects and indeed stopped the spread of the otherwise tainted plantlife.
All this changed when Steve was born, for he was gifted with something no other Sapient had to date displayed... Ambition.
Steve wasn't content with the wandering hunter/gatherer lifestyle of most humans in Terraria. Steve could tell something was not quite right about Terraria and he resolved to discover its secrets!
-Game Start-
Edit: Maybe I should make this into an LP.