TribeTwelve started off as an innocent little thing, a YouTube page for Noah Maxwell's project on the Twelve Tribes of Israel. However, soon afterward, the project was cancelled by the teacher for unknown reasons. The news became worse when Noah received word that his childhood friend and closest cousin, Milo Asher, was found dead in his room, killed by a "suicidal" drug overdose. Noah wanted to change the page from a project page to a dedication page, so Milo would be remembered. However, as he watched the videos, he noticed things...things he never saw before, but Milo did.
Something that terrified him.
TribeTwelve is yet another chapter of the Slender Man Mythos, similar in vein to Marble Hornets. Noah documents himself after finding something much worse in his videos. As per Slender Man videos, it's...pretty frightening.