In the book Singularity Sky [0], mankind invented the first time-looped computer, and it cycled up to a godlike overlord. After making a lot of very disruptive changes (which of course seem to be immediate to everyone else) it seems to have become surprisingly disinterested or uninvolved.
Anyway, it has only one hard "commandment": Nobody can violate causality anywhere inside its own historic light-cone, since doing so could be a potential attack (or competition) to its own existence.